Cephalosporins Can Be Used in Penicillin Allergy

Did you know the literature describing the cross-reactivity between cephalosporins and penicillins is 30-40 years old?  It sort of takes the "modern" out of "modern medicine."

At any rate, this is a literature review that aims to update the classical teaching that cross-reactivity between cephalosporins and PCN is ~10%.  They identified 406 articles on the topic and distilled it down to 27 respectable articles for inclusion in summary.  They rate the quality of the articles, and, unfortunately, find only a few good or outstanding articles and a preponderance of adequate evidence.

But, essentially, what they find is the cross-reactivity boils down to the presence of a shared R1 side chain present on first-generation and some second-generation cephalosporins.  Specific first-generation cephalosporins, such as cefadroxil (Duracef), were seen to have up to 28% cross-reactivity in some series, though the typical rate was lower, down to 0.11% with cefazolin (Ancef).  The largest meta-analyses estimated the true cross-reactivity at ~1% rather than 10%, with most of these occurring with first-generation cephalosporins.

In summary - 3rd-generation and greater cephalosporins with disimilar R1 side chains can probably be used in appropriate clinical situations despite a PCN allergy without incidence of allergy greater than in those patients who do not have a documented PCN allergy.

"The use of cephalosporins in penicillin-allergic patients: A literature review."

www.ncbi.nlm.nih.gov/pubmed/21742459

Everyone Is On the Cardiac CT Bandwagon

The NEJM is on the wagon with their recent publication.  Annals of EM has been publishing all the ROMICAT trials.  And, not to be outdone, the American College of Cardiology is publishing the CT-STAT trial - a head to head comparison between coronary CT angiogram in the Emergency Department and stress perfusion imaging.

The endpoint of interest, however, is length of stay - and by association total index visit costs - rather than accuracy or safety.  And, in this sense, it was successful.  The primary difference in LOS was the length of time it took to perform the CT or stress test, which was approximately 4 hours quicker in the CT group.  ED costs were also lower, somehow, presumably billing for an observation code while awaiting the stress test and results.

However, what the authors don't include are the total downstream costs and time of additional testing after the Emergency Department visit.  The stress test group had 34 abnormal or non-diagnostic scans, while the CT group had 64.  27 patients in the stress group underwent additional testing vs. 51 in the CT group - mostly stress tests that were subsequently normal - and none of these costs or times are included in their analysis.  I imagine if these extra tests are included in their analysis, the cost difference shrinks or disappears.

It seems to be a trend to advertise more than CT angiography actually delivers.

Several authors are sponsored by Siemens.

"The CT-STAT (Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment) Trial"
www.ncbi.nlm.nih.gov/pubmed/21939822

Dabigatran - In Annals of Internal Medicine

My short review article warning the internists of the dangers associated with rushing into overuse of dabigatran was published today in Annals of Internal Medicine.


It was actually originally entitled "Dabigatran – Sinking Into Uncharted Waters," but the editor changed it after the Italian cruise ship disaster.


"Dabigatran — Uncharted Waters and Potential Harms"
http://www.annals.org/content/early/2012/05/23/0003-4819-157-1-201207030-00467

ADAPT 2-Hour Rule Out

I've had a couple questions recently about accelerated rule-out strategies - considering they're in the ACEP Guidelines, but the AHA seems to endorse a viewpoint that any suspicion for cardiac chest pain needs to be taken to its bitter end with a provocative test.  Unfortunately, an all-in strategy doesn't mesh quite as well with reality where the costs are astronomical, and the yield abysmal.

Conveniently, this is another recent study highlighting the use of two sets of biomarkers, two hours apart - using conventional troponin assays.  This is an observational cohort study in Australia and New Zealand investigating the feasibility of their stratification instrument, with the endpoints of "Major Adverse Cardiac Events" within 30 days - an endpoint that, for once, excludes revascularizations.  Specifically, the decision protocol being evaluated includes:
 - Negative troponins at 0 and 2 hours from presentation.
 - No new ischemic changes on ECG.
 - TIMI Score of zero.

Of their 1,976 enrolled patients, 392 met these criteria and were followed for 30 days.  Their single miss was reported as an nSTEMI with two initially negative troponins who subsequently had a positive 12-hour troponin.  Therefore, their sensitivity for 30-day MACE is statistically 98.1% to 99.9%.  This is one of the eight patients in the low-risk cohort who underwent a revascularization procedure in the course of their routine care.

Essentially, using a normal EKG, two negative sets of enzymes, and a risk-stratification instrument - TIMI, Geneva, etc. - the evidence out there lets you have a discussion with the patient regarding their overall risk for a poor outcome.  If you're stuck in a zero-miss environment, then any of these 2-hour protocols will be of no use - they all have a non-negligible miss rate.  But, if you have a grey area to work with, and an otherwise relatively low-risk patient, a quick two-hour troponin helps you catch a few extra fish you otherwise would have missed.

"2-Hour Accelerated Diagnostic Protocol to Assess Patients With Chest Pain Symptoms Using Contemporary Troponins as the Only Biomarker The ADAPT Trial"
www.ncbi.nlm.nih.gov/pubmed/22578923