Tuesday, September 13, 2011

Predicting Poor-Performing Residents

This is an entertaining look into the residency training experience in the United States, which is renowned for its brutality in certain specialities.  As far as sleep-deprivation goes, it ranks right up there with some of the lowest quality of life professional jobs.

This is, basically, the quality-of-life information from the Internal Medicine in-service training examination, as reported in JAMA.  The authors have linked it to in-training examination results for the, probably predictable, association of poor work/life balance and poor in-training scores.

Interesting tidbits I noticed:
 - 15.3% of residents stated that life was as good as it could be.
 - PGY-1 and PGY-2 residents had nearly equal poor quality-of-life and work/life balance - which improves significantly PGY-3.
 - Over 40% of residents have >$100,000 in debts - and that was associated with poorer quality-of-life scores.
 - Improvements in quality-of-life for PGY-3 was mirrored by a corresponding increase in depersonalization.

Not a healthy experience, by a longshot.  Pity those whose residencies are longer than the bare minimum of 3 years.

"Quality of Life, Burnout, Educational Debt, and Medical Knowledge Among Internal Medicine Residents."

Sunday, September 11, 2011

More Platelets In Massive Transfusion

Where are we going to get all these blood products?  The rapidly growing body of literature backing early transfusion of FFP and platelets in massive transfusion protocols continues to tilt towards the 1:1:1 ratio.

This is a retrospective review of whether platelet transfusion impacts survival in trauma.  They identify three categories of ratios of platelets to RBCs (>1:20, 1:2, and 1:1) and measure a variety of different outcomes.  Briefly, more platelets helped with survival to 24 hours, but more platelets also increased multi-organ failure.  In the end, the initial survival differences were great enough that they outweighed the additional multi-organ failure for a significant survival benefit (52% vs. 57% vs. 70%).

They exclude 25 patients who died within an hour in an effort to mitigate survival bias.  However, looking at the breakdown of survival times, it looks as though almost all the mortality benefit to increased platelet ratios was realized in the first 6 hours - and then the mortality numbers worsen in tandem after that.  The authors state they were unable to truly quantify retrospectively whether the patients survived because they received more platelets vs. whether patients surviving longer were able to receive more platelets, and note that prospective trials will need to be performed.

I would also note that a significant portion of their high ratio patients also received Factor VII, for whatever that's worth.

So, we continue to await high quality prospective trials that specifically address the impact of survival bias.

"Increased Platelet:RBC Ratios Are Associated With Improved Survival After Massive Transfusion."
http://journals.lww.com/jtrauma/Abstract/2011/08003/Increased_Platelet_RBC_Ratios_Are_Associated_With.2.aspx

Saturday, September 10, 2011

Impedance Threshold Devices Are Useless

So, supposedly, impedance threshold devices installed inline for ventilation during CPR potentially improve hemodynamics via negative intrathoracic pressure.  This is a prospective, randomized, multi-center, placebo-controlled sham study that really meets a very high standard for internal validity.  Over 4000 patients in the ITD group, the sham ITD group, and the not-enrolled comparison cohort.

Short summary:
 - Minimal differences between groups.
 - 27.8% sham vs. 27.1% active device ROSC in the ED.
 - 8.2% sham vs. 8.2% active device discharge from the hospital.
 - No apparent harms from the ITD device, but no benefits either.

The most important point from this article is that we have gotten sloppy in our rush to implement supposedly new and beneficial therapies in medicine.  Hypothermia, TPA for stroke, Factor VIIa, direct thrombin inhibitors, etc. and we should add impedance threshold devices to the list.  The AHA has had ITD as a class IIa recommendation to improve hemodynamics since 2005 - six years of useless therapy and costs based solely on a theoretical model without proof of improved outcomes.  Hammering this point home never gets old.

"A Trial of an Impedance Threshold Device in Out-of-Hospital Cardiac Arrest."
www.ncbi.nlm.nih.gov/pubmed/21879897

Friday, September 9, 2011

More Mistakes In An Unfamiliar System

Probably tells us what we already know - and likely underestimates the problem.

These authors take a retrospective look at all the reported medication errors between 2000 and 2005, and then try to associate increased errors with the involvement of a temporary staff member.  The problem is, they don't actually have staffing documents that report which employees are temporary - they rely on the population of a QA field listing "contributing factors", under which temporary staff is an option.  So, you can dismiss this as a bit of garbage-in/garbage-out depending on how accurate the reporting is - but, I figure, if anything, people will forget to implicate temporary staffing more frequently than not.

More interesting - and potentially confounding re: temporary vs. permanent - are the perceived reported reasons behind the medication error.  Temporary staff were more likely to be reported to have knowledge deficits, performance deficits, and fail to follow appropriate procedures.  I might read into that data that it's easier for an unfamiliar temp to appear knowledge-deficient, although that's just my own imagination.

From a risk management standpoint, the solution seems to be: whatever the retention costs of your permanent staff members, they are almost assuredly lower than the costs associated with the errors inflicted upon patients by temps.

"Are Temporary Staff Associated with More Severe Emergency Department Medication Errors?"

Wednesday, September 7, 2011

Epinephrine Neither Wins Nor Fails

The crux of the problem - epinephrine continues to improve short-term ROSC with uncertain long-term outcome improvement.

This is a prospective out-of-hospital arrest study from Australia in which epinephrine or saline placebo was given to patients during resuscitation by EMS.  And, like many studies before it, it fails to show a meaningful difference between patients receiving epinephrine and patients receiving placebo.  Rather, their primary outcome of survival to hospital discharge had 1.9% with placebo and 4.0% with epinephrine - but this result was not statistically significant with a p-value of 0.15.

Of course, what the lack of statistical significance means in this case is that this difference could have occurred by chance 15 times out of 100 times they performed this study - which, while not meeting the gold standard of 5 out of 100, is still a reasonably interesting clinical trend.  Like all studies before it, the short-term endpoints met statistical significance, including ROSC of 8.4% for placebo and 23.5% for epinephrine.  There are a few confounding differences between groups: more placebo patients had witnessed arrest, although the number with bystander CPR was the same; more placebo patients were endotracheally intubated in the field, which usually confers a survival disadvantage; and more epinephrine patients were ultimately transported to the hospital from the field.

So, there's two ways to look at it: 1) epinephrine works, and we just need to figure out how to salvage more of those ROSC or 2) epinephrine is flogging far too great a number of lost husks back to life that will go on to consume ICU resources and expire regardless.

But, if we're not going to give epinephrine, how do we otherwise look busy during a code?  And, what happens downstream to our epinephrine ROSC that fail to leave the hospital or the ER, and can we prevent it?

I am still not sure what the right answer is - like many diseases, cardiac arrest patients are a heterogenous group in which there is almost certainly a subset of patients that benefits from epinephrine, but we don't yet know who that might be.

"Effect of adrenaline on survival in out-of-hospital cardiac arrest: A randomised double-blind placebo-controlled trial."
www.ncbi.nlm.nih.gov/pubmed/21745533

Thanks to @cliffreid of Resus M.E! for first noting this article.

Tuesday, September 6, 2011

Sternal IO is the Best IO

All our cardiac arrest patients roll in these days with an IO in place - and we are full proponents of rapid, successful access in the uncontrolled field environment.  But, how effective is it really in the CPR situation?

So, this is an animal study that tries to address the theoretical efficacy of intraosseous access versus central venous access.  They use injection of dye tracers into Yorkshire swine for a comparison between intraosseous sternal, intraosseous tibial, and external jugular central venous cannulation.

Unfortunately, this is a good news/bad news study.  The good news - peak concentrations were achieved only slightly more slowly in the arterial circulation following sternal intraosseus injection than the gold standard central venous injection.  And, the peak concentrations were nearly identical.  Bad news, the tibial IO was half the speed and half the arterial peak concentration of the sternal IO.

In theory, this is of relative importance depending on which medication you're using - presumably the speed of administration matters in CPR and peak concentration may matter as well.  Of course, this is limited as 1) pigs and 2) efficacy vs. effectiveness, because they're not measuring clinical outcomes.

But it's interesting to worry about.  Too bad it's hard to do chest compressions with your access point where your hands are supposed to go.  It would be interesting to compare this result to a humeral head IO.

"Pharmacokinetics of Intraosseous and Central Venous Drug Delivery During Cardiopulmonary Resuscitation."
http://www.ncbi.nlm.nih.gov/pubmed/21871857

Sunday, September 4, 2011

New Pediatrics UTI Guidelines


For children between 2 and 24 months of age, the relevant high points for EM:
 - Don't use bag urines.  Catheterization or suprapubic aspiration is the only acceptable way to make a diagnosis.  However, if you're stuck, and you have to use a bag, a completely normal bag urine is diagnostic.
 - Send a culture to definitively establish the diagnosis based on pyuria and/or bacteruria and the presence of at least 50,000 CFU/mL of a uropathogen.
 - Oral antibiotic recommendations listed include amoxicillin-clavulanate, trimethoprim-sulfamethoxazole, and a range of oral cephalosporins for at least 7 days.  They do not have any evidence to compare 7, 10, and 14 day courses.  Nitrofurantoin is not appropriate.

Nothing terribly earthshaking - seems all pretty reasonable.

"Urinary Tract Infection: Clinical Practice Guideline for the Diagnosis and Management of the Initial UTI in Febrile Infants and Children 2 to 24 Months."
pediatrics.aappublications.org/content/early/2011/08/24/peds.2011-1330

Saturday, September 3, 2011

When Does a Repeat Head CT Have Value?

Not practice-changing, but an interesting observational report regarding when these authors found value in performing a repeat head CT after minor head trauma.

Specifically, they looked at a subgroup of patients whose initial head CT was normal after blunt trauma, but received a repeat head CT an average of ~8 hours later for an abnormal neurologic examination.  These abnormal neurologic examinations were further stratified into three groups - a "persistently abnormal" exam, a "acute deterioration" in neurologic examination, and a catchall "unknown" group.  The first two groups had mean GCS of 12.4 and 14.5 - but the reason why the "unknown" group is what it is - their average GCS is 4.

They found that repeating the head CT in the 61 patients they had with persistently abnormal neurologic examinations did lead to some worsening of the initial findings - but did not change management in any cases.  However, 6 of the 21 patients who had an acute deterioration had a change in management, as well as 1 patient in the unknown group.

Small sample, but interesting, nonetheless.

"Utility of Repeat Head Computed Tomography in Patients With an Abnormal Neurologic Examination After Minimal Head Injury."
www.ncbi.nlm.nih.gov/pubmed/21857258

Thursday, September 1, 2011

When Is Blunt Chest Trauma Low-Risk?

According to this study, always - but rarely.

This is a prospective 3-center trauma study attempting to discern clinical variables that predicted the absence of serious traumatic chest injury in the setting of blunt trauma.  2,628 subjects enrolled, with 271 of them diagnosed with a serious injury - pneumothorax, hemothorax, great vessel injury, multiple rib fractures, sternal fracture, pulmonary contusion, and diaphragmatic rupture.  They do a recursive partitioning analysis and identify a combination of seven clinical findings that had a 99.3% (97.4 - 99.8) sensitivity for serious traumatic injuries.

But, I might be missing the point of this instrument a little bit.  Only 10% of their cohort had a traumatic injury - yet out of the remaining 90% without serious traumatic injury, their rule could only carve out 14% as low risk.  These low risk patients, the authors then propose, obviates any chest imaging at all.  While I am all for reducing unnecessary testing, this seems like an awfully low yield decision rule.  Yes, this study identifies young patients who are perfectly fine after a low-risk blunt trauma and do not need even an x-ray - but I'd really rather see more work preventing some of the 584 chest CTs performed in this cohort.  Additionally, their criterion standard for negative imaging is inadequate - most received CXR alone and there's no follow-up protocol to test for possible missed injuries, whether clinically significant or not.

Considering the criteria they identified, it seems they could almost get equal or greater reduction in imaging if the clinicians were simply a little more thoughtful with respect to knee-jerk imaging in trauma.

"Derivation of a Decision Instrument for Selective Chest Radiography in Blunt Trauma."
www.ncbi.nlm.nih.gov/pubmed/21045745

Wednesday, August 31, 2011

iPhone Medical Apps To The Rescue

In this study, the author and creator of "PICU Calculator" for iPhone details the superiority of a medical student with a smartphone over an attending using the pharmacy reference book.  A few entertaining tidbits from their main results:
 - Medical students don't know how a book functions - failed to correctly complete any pediatric dosing task using the British National Formulary for Children.
 - Residents and attendings managed to make the book work for them about half the time.
 - Overall across all levels of training, 35 for 35 in correct dosage and volume using the iPhone app - with a mean time savings of over 5 minutes.

So, when the author of an iPhone app choses a clinical task his app is designed to replace, it works great!  But, the larger point - as we already knew - there is a role for well-designed point-of-care electronic tools, so we shouldn't give up on our CPOE and EHR kludge so soon.

"Students prescribing emergency drug infusions utilising smartphones outperform consultants using BNFCs."
www.ncbi.nlm.nih.gov/pubmed/21787737

Monday, August 29, 2011

Who Are The Readmitted?

Now, where I trained, we were the only useful facility for hundreds of miles - so we actually had a a lot of continuity of care in the Emergency Department.  And nothing beat the continuity we saw when a patient who was discharged in the morning was back in our Emergency Department by evening - and the inevitable question of "how did they screw this up?"

This is a retrospective look at the readmissions from 11 teaching and community hospitals trying describe the readmissions as avoidable vs. unavoidable, characterize the cause for readmission, and see if there were any baseline characteristics that might predict readmission.  They found avoidable readmissions were in the minority, and there was no useful predictive clinical information regarding baseline differences between the readmitted group and the overall cohort - comorbidities, length of stay, new medications, etc.  When patients were avoidably readmitted, however, several recurring factors were noted:
 - Management error (48% of the time)
 - Surgical complications (38.5%)
 - Medication-related event (32.7%)
 - Nosocomial infection (18.3%)
 - System error (15.4%)
 - Diagnostic error (10.6%).

Considering CMS is looking closely at decreasing payments to physicians and hospitals for readmissions, this study provides a small amount of systematic insight into some of the things we've all observed anecdotally.

"Incidence of potentially avoidable urgent readmissions and their relation to all-cause urgent readmissions."
www.cmaj.ca/content/early/2011/08/22/cmaj.110400

Sunday, August 28, 2011

Good Thought, But It's Not Pertussis

A Swiss study in which only 2.5% percent of 1,049 pediatric ambulatory and hospitalized patients presenting with a cough-illness and who were tests for pertussis were culture positive for B. pertussis or parapertussis.  Probably a relatively accurate picture of the general prevalance of pertussis in a non-outbreak situation.  They additionally report that viral superinfection is rare enough to be coincidental - 0.6% - although the authors do note other studies have reported higher incidence, particularly in RSV+ hospitalized children <6 months of age.

So, this data is out the window if there's an outbreak situation, but the overall clinical take home is that, yet again, our index of suspicion may be too high for an infrequently diagnosed condition - and we should moderate testing in the lower acuity cases.

"Bordetella pertussis and Concomitant Viral Respiratory Tract Infections are Rare in Children With Cough Illness."
www.ncbi.nlm.nih.gov/pubmed/21407144

Friday, August 26, 2011

Malpractice Risk in Emergency Medicine

I was actually surprised by these statistics - I expected Emergency Medicine to be higher.  After all, we're meeting people with potentially unrealistic expectations, suffering long wait times, without continuity of care, and potential bad outcomes lurking everywhere.

But, really, our claims against and claims with payout are really pretty much average across specialties.  Neurosurgery and Thoracic Surgery are the nightmare specialties, where nearly a 5th of physicians practicing in those specialties has a claim filed against them each year.  Another interesting statistic was that Gynecology, only a little above average in claims filed against, has the highest percentage of payouts.

Neurosurgery, Neurology, and Internal Medicine lead the way in median payout, but Pediatrics, Pathology, and Ob/Gyn lead the way in mean payout - apparently skewed by the occasional massive award.

Given the legislation pending in many states these days giving additional protections to Emergency Physicians and physicians on-call to Emergency Departments, it's really not a bad time to be in EM, from a liability standpoint.

"Malpratice Risk According to Physician Specialty"
www.ncbi.nlm.nih.gov/pubmed/21848463

Thursday, August 25, 2011

Forced Diuresis Prevents CIN

I admit, I was shocked when I got to the end of the paper and found the authors had no disclosures - it seems nearly every study concerning a commercial product has someone on the payroll.  Heck, the study is even registered with clinicaltrials.gov, and they didn't change their protocol at all.

Anyway, this paper is in regards to the RenalGuard system, which is basically a closed-loop system that replaces a furosemide forced diuresis with normal saline.  They compare this to "usual therapy", which, for them, is sodium bicarbonate and n-acetylcysteine (NAC) for the prevention of contrast-induced nephropathy as a result of some iodixanol contrast load.  Basically, they ran this system through a few patients who were at high-risk for CIN for ~5 hours around the time of their contrast procedure and tried to get their urine flow rate >300 mL/hr.  When successful, those patients had significantly less CIN than the "usual therapy" group (10% vs. 20%).

So, seems like it works.  There was more pulmonary edema (3 vs. 1) in the RenalGuard system, and more electrolyte abnormalities to replace, but this is a therapy that might yet have some utility.  It may even be practical in an ED setting, to a limited extent.

"Renal Insufficiency After Contrast Media Administration Trial II (REMEDIAL II)"
www.ncbi.nlm.nih.gov/pubmed/21518686

Tuesday, August 23, 2011

The PERC Rule Mini-Review

Journal club this month at my institution involved the literature behind the derivation and validation of the PERC (Pulmonary Embolism Rule-Out Criteria) Rule.  So, as faculty, to be dutifully prepared, I read the articles and a smorgasbord of supporting literature - only to realize I'm working the conference coverage shift.  Rather than waste my notes, I've turned them into an EMLit mega-post.

Derivation
The derivation of the PERC rule in 2004 comes from 3,148 patients for whom "an ER physician thought they might have Pulmonary Embolism".  Diagnosis was confirmed by CTA (196 patients), CTA + CTV (1116), V/Q (1055) + duplex U/S (372), angiography (11), autopsy (21), and 90-day follow-up (650).  348 (11% prevalence) were positive for PE.  They then did a regression analysis on those patients and came up with the PERC rule, the eight-item dichotomous test for which you need to answer yes to every single question to pass.

The test case for the derivation came from 1,427 "low-risk" patients that were PE suspects, and as such, had only a d-Dimer ordered to rule-out PE - and in whom a CTA was performed when positive.  114 (8% prevalence) had PE.  There was also an additional test case of "very low-risk", 382 patients from another dyspnea study who were enrolled when "an ED physician thought PE was not the most likely diagnosis."  9 (2.3%) of the very low-risk cohort had PE.

Performance on their low-risk test set was a sensitivity of 96% (CI 90-99%) with a specificity of 27%.  On their very low-risk test set, sensitivity was 100% (59-100%) with a specificity of 15%.

Validation
Multicenter enrollment of 12,213 with "possible PE".  8,183 were fully enrolled.  51% underwent CTA, 6% underwent V/Q, and everyone received 45-day follow up for a diagnosis of venous thromboembolism.  Overall, 6.9% of their population was diagnosed with pulmonary embolism.

Of these, 1,952 were PERC negative - giving rise to a 95.7% sensitivity (93.6-97.2%).  However, the authors additionally identify a "gestalt low-risk" group of 1,666 that had only 3.0% prevalence of PE, apply the PERC rule to that, and come up with sensitivity of 97.4% (95.8 - 98.5%).

The authors then conclude the PERC rule is valid and obviates further testing when applied to a gestalt low-risk cohort in which the prevalence is less than 6%.

Other PERC Studies
Retrospective application of PERC to another prospective PE database in Denver.  Prevalence of PE is 12% of 134 patients.  Only 19 patients were PERC negative, none of whom had PE.  Sensitivity is 100% (79-100%).

Retrospective application of PERC to patients receiving CT scans in Schenectady.  Prevalence of PE was 8.45% of 213.  48 were PERC negative, none of whom had PE.  Sensitivity is 100% (79-100%).

Effectiveness study of PERC in an academic ED (Carolinas).  183 suspected PE patients, PERC was applied to 114, 65 of whom were PERC negative.  16 of the PERC negative underwent CTA, all negative.  14 day follow-up of the remaining 49 also indicated no further PE diagnosis.  No sensitivity calculation.

Retrospective application of PERC to prospective PE cohort in Switzerland.  Prevalence of PE was 21.3% in 1,675 patients.  In the 221 patients who were PERC negative, 5.4% had PE (3.1 - 9.3%) for a sensitivity of 96.6 (94.2 - 98.1%).  The subset of PERC negative who were also low-risk by Geneva Score actually had a higher incidence of PE at 6.4%.

Summary
So, PERC can only be applied to a population you think is low-risk for PE - for which you can use clinical gestalt or Wells' - because it looks like Wells low-risk is 1.3% (0.5-2.7%) to 2% (0-9%).  But, you can't use Geneva because that prevalence is closer to 8% for low-risk - and that's essentially what the Swiss study shows.

But in this already very low-risk population, the question is, what is the role of PERC?  Clinical gestalt in their original study actually worked great.  Even though clinicians were only asked to risk stratify to <15%, they risk stratified to 3.0% prevalence of PE.  Which, of course, means our estimation of the true risk of pulmonary embolism is absolutely bonkers.  If you take a gestalt or Wells' low-risk population, apply PERC, and it's negative - your population that nearly universally didn't have a PE still doesn't have a PE, and it doesn't get you much in absolute risk reduction.  You probably shouldn't have even considered PE as a diagnosis other than for academic and teaching reasons if they're Wells' low-risk and PERC negative.

Then, if you take the flip side - what happens if your patient is PERC positive?  You have a low-risk patient whose prevalence for PE is probably somewhere between 1 and 5%, and now you've got a test with a positive LR of 1.24 - it barely changes anything from a statistical standpoint.  Then, do you do a d-Dimer, which has a positive LR between 1.6 and 2.77?  Now you've done a ton of work and painted yourself into a corner and you have to get a CTA on a patient whose chance of having a PE is still probably less than 10%.

That's where your final problem shows up.  CTA is overrated as a diagnostic test for pulmonary embolism.  In PIOPED II, published 2006 in NEJM, CTA had 16 false positives and 22 true positives in their low risk cohort - 42% false positive rate - and this is against a reference standard for which they estimated already had a 9% false positive and 2% false negative rate.  CTA is probably better now than it once was, but it still has significant limitations in a low-risk population - and I would argue the false positive rate is even higher, given the increased resolution and ability to discern more subtle contrast filling defects.

So, this is what I get out of PERC.  Either you apply it to someone you didn't think had PE and it's negative and you wonder why you bothered to apply it in the first place - or you follow it down the decision tree and you end up at a CTA for whom you can flip a coin to believe whether the positive result is real or not.

And, I don't even want to get into the clinical relevance of diagnosis and treatment of those tiny subsegmental PEs we're "catching" on CTA these days.

"Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism"
www.ncbi.nlm.nih.gov/pubmed/15304025

"Prospective multicenter evaluation of the pulmonary embolism rule-out criteria"
www.ncbi.nlm.nih.gov/pubmed/18318689

"Assessment of the pulmonary embolism rule-out criteria rule for evaluation of suspected pulmonary embolism in the emergency department"
www.ncbi.nlm.nih.gov/pubmed/18272098

"The Pulmonary Embolism Rule-Out Criteria rule in a community hospital ED: a retrospective study of its potential utility"
www.ncbi.nlm.nih.gov/pubmed/20708891

"Prospective Evaluation of Real-time Use of the Pulmonary Embolism Rule-out Criteria in an Academic Emergency Department"
www.ncbi.nlm.nih.gov/pubmed/20836787

"The pulmonary embolism rule-out criteria (PERC) rule does not safely exclude pulmonary embolism"
www.ncbi.nlm.nih.gov/pubmed/21091866

"Multidetector Computed Tomography for Acute Pulmonary Embolism"
www.ncbi.nlm.nih.gov/pubmed/16738268

"D-Dimer for the Exclusion of Acute Venous Thrombosis and Pulmonary Embolism"
www.ncbi.nlm.nih.gov/pubmed/15096330

http://www.mdcalc.com/perc-rule-for-pulmonary-embolism

Monday, August 22, 2011

ACI-TIPI For Predicting Cardiac Outcomes

In an earlier post, I noted an article that had done a systematic review finding 115 publications attempting to create or validate clinical prediction rules for chest pain.  Well, here's number 116.

The ACI-TIPI (Acute Cardiac Ischemia Time-Insensitive Predictive Instrument) is computerized analysis software that generates a score regarding the likelihood of cardiac ischemia based on age, gender, chest pain and EKG variables.  It's actually a product marketed and sold by Philips.  These authors tried to evaluate how predictive this instrument was for predicting 30-day events, with an interest in identifying a group that could be safely discharged from the Emergency Department.

In an institution with 55,000 visits a year, the authors recruited only 144 chest pain patients - which is the first red flag.  It doesn't matter how good your prediction rule is if you only recruit 144 patients - your confidence intervals will be terrible, and their sensitivities for identifying 30 day cardiac outcomes are 82-100% at best.  And, yes, they did say if the ACI-TIPI score is <20, it had a purportedly useful negative predictive value.

So, I suppose this paper doesn't really tell us much - and even if the data were better, I'm not sure the sensitivity/specificity of this ACI-TIPI calculation would meet a useful clinical threshold to reduce low-risk hospitalizations any better than clinical gestalt.  I'll be back with you when I find risk-stratification attempt 117....

"Prognostic utility of the acute cardiac ischemia time-insensitive predictive instrument (ACI-TIPI)"
www.intjem.com/content/4/1/49

Saturday, August 20, 2011

Sometimes, The Pregnancy Test Lies

A couple years ago, my hospital pulled the POC urine pregnancy tests from the ED because of false negatives - leading to incredulous discussions of how it was possible for a nursing assistant to screw up something so simple as a dichotomous colormetric test.

Well, at Washington University, when they had multiple issues with their POC pregnancy test, they investigated the issue in more depth, and this nice little article is an overview of the limitations of the the test.  There are two ways the POC test fails:
 - Not pregnant enough.
 - Too pregnant.

We all know about sensitivity in early pregnancy really only being 97% or so at one week, and no one will fault the test for that.  However, their case series of five patients, all of whose serum hCG was >130,000, are hypothesized to have saturated the reagent to the point of a false-negative test.

In any event, interesting article about something I hadn't put much thought into.

"'Hook-Like Effect' Causes False-Negative Point-Of-Care Urine Pregnancy Testing in Emergency Patients"
http://www.ncbi.nlm.nih.gov/pubmed/21835572

Friday, August 19, 2011

CT Coronary Angiography Proves People WIth CAD Die Sooner

This is a neat study that followed up 23,854 patients from a multicenter CTCA registry - the CONFIRM registry - over three years to evaluate their long term prognostic risk.  And - amazingly enough - the patients who had no coronary artery disease identified on their CTCA had an annualized rate of 0.28% of death from all causes.  Which seems pretty impressive, and it's better than the people who had non-obstructive and various types of obstructive CAD on their CTCA.

But then, the hazard ratios for patients who had 3-vessel and left main disease on their CTCA was still only as high as six times more likely than the no CAD cohort - which is a lot higher in relative terms, but still not very high in absolute terms - and there were a lot of other comorbidities in these patients that would contribute to their all-cause mortality from non-cardiac causes.  So, yes, not having CAD - as well as being a generally healthy person - helps you live longer.

The question still remains where CTCA fits into an Emergency Department evaluation for chest pain.  We are seeing more and more research now that primary PCI for asymptomatic lesions isn't any survival benefit over medical management - so identifying these lesions and admitting these patients to cardiology for intervention isn't going to be in our future.  Considering over 55% of their cohort had either non-obstructive or obstructive disease found, now you're going to be on the hook for making outpatient CAD risk-modification decisions after cardiology declines them.

Whether CTCA is used should be a standardized, institution-wide decision, because I don't think anyone wants to take the weight of sorting through all this evidence and risk/benefit ratios as a lone wolf.

"Age- and Sex-Related Differences in All-Cause Mortality Risk Based on Coronary Computer Tomography Angiography Findings"
www.ncbi.nlm.nih.gov/pubmed/21835321

Wednesday, August 17, 2011

CT Use Is Increasing(ly Justified?)

Retrospective cohort analysis based off the NHAMCS dataset, with all the inherent limitations within.

We have a 330% increase in the use of CT in the Emergency Department - up from 3.2% in 1996 to 13.9%  in 2007.  This increase is pretty stable across all age groups (including a rate of up to nearly 5% now in patients under 18 years of age).  The interesting part of the paper that's something we didn't already know, is their data regarding the adjusted rate of hospitalization or transfer after receiving CT.  In 1996, 26% of patients receiving a CT were admitted to the hospital, while now only 12% of patients receiving CT are admitted to the hospital.

The problem is, I've seen news organizations running with the conclusion: CT rates might be higher, but since the relative risk of hospitalization is lower after a CT, therefore, it must be preventing hospitalizations.  But, you can't draw any such conclusion from the data - particularly considering hospitalizations have climbed over that same period.

We just aren't seeing any data that links the increase in CT use to improved outcomes.  Increased CT usage certainly has its place as the standard of care in many instances, but there's no silver lining to this 330% increase.

"National Trends in Use of Computer Tomography in the Emergency Department."
www.ncbi.nlm.nih.gov/pubmed/21115875

Tuesday, August 16, 2011

Viral or Bacterial Infection? A Blood Test

This is another "someday, in the future" article that made the rounds with the news releases yesterday - where, supposedly, within a few hours of infection, there are significant differences in phagocyte chemiluminescence that allow researchers to differentiate between viral and bacterial infections.

As usual, the breathless commentary is a little ahead of the actual research results.  What the authors did was a data-mining experiment from 69 patients, each of whom had been diagnosed (through standard clinical practice) with either a viral infection, or a bacterial infection.  They ran all the polymorphonuclear leukocytes through their assay, recorded several different sorts of chemoluminescence, and then let computer software do a partitioning analysis to determine the most predictive patterns for bacterial and viral infections.

The software trained to 94.7% accuracy on the "knowns", and then, when tested on a confusion sample with 18 "unknowns" it was 88.9% accurate.

So, still not good enough for clinical use as a dichotomous result, but if it were allowed to return an equivocal range that quantified the assay uncertainty, then perhaps it could have a role in clinical practice.  In theory, an assay such as this might otherwise reduce additional testing and help reduce the number of viral infections that receive antibiotics.

"Differentiation Between Viral and Bacterial Acute Infectious Using Chemiluminescent Signatures of Circulating Phagocytes"
http://www.ncbi.nlm.nih.gov/pubmed/21517122

Sunday, August 14, 2011

Tranexamic Acid - Critique of CRASH-2


These authors review the literature regarding TXA and it's cost/risk/benefit for hemostatic control of injured trauma patients.  Of course, this specifically means they review the single significant piece of literature for TXA - the CRASH-2 trial published in the Lancet.

I'm not sure I entirely agree with their premise that TXA is safer because it is just an antifibrinolytic rather than an activator of clotting/platelet aggregation - clot formation and breakdown is a dynamic process and any interference in that system carries a risk.  But, they do a fairly detailed look at TXA and the CRASH-2 trial, and I think they make a fair and defensible point that, while the NNT is pretty high, it is a fairly low cost intervention with a relevant outcome variable of overall mortality.

While a study with 20,000 patients is a nice start, I'd still like to see at least one other prospective study replicating similar results with an appropriate safety analysis.

"Tranexamic Acid for Trauma Patients: A Critical Review of the Literature"
www.ncbi.nlm.nih.gov/pubmed/21795884