Month: July 2019

CRP for COPD

If you follow this blog, you’ve probably read various critiques of the use of procalcitonin to guide antibiotic prescribing. Procalcitonin, a non-specific inflammatory marker, provides a small amount of informational value regarding the underlying etiology of infection, but my underlying criticism of its envisioned use is:

  • The baseline rate of antibiotic prescribing is so poor, and the likelihood of poor outcomes so low, a safe reduction in prescribing is guaranteed.
  • It provides about the same area-under-the-curve for predicting bacterial etiologies as C-reactive protein.
  • The pro-procalcitonin studies and contributions are effectively covered in the fingerprints of the manufacturers of the assay.

So, then, replace the above complaints with – well, mostly just the top one, because here we are with CRP doing the same things for which procalcitonin is advertised, and the apparent conflict-of-interest is turned down a few notches.

In this study, 86 primary care clinics in England and Wales randomized patients with a diagnosis of COPD and a clinical diagnosis of an acute exacerbation to use of point-of-care CRP testing versus usual care. Similar to those studies seen with procalcitonin, prescribers were provided guidance with respect to various CRP levels and recommendations for either prescribing, possible prescribing, or do not prescribe. The primary outcome and secondary outcomes were associated with receipt of any antibiotics, quality of life, and adverse health outcomes.

Over the course of two years, 649 patients were randomized to the two arms, with a handful of each failing to properly undergo initial study procedures. The prescribing rate at the index visit in the “usual care” group: 69.7%. The prescribing rate with CRP: 47.7%. A winner is CRP!

Except that 76% of patients had CRP less than the threshold at which antibiotics were recommended. Another 12% were in the “antibiotics maybe” group. Thus, nearly 90% of the entire cohort were suspected of having no or limited benefit to antibiotics – so, of course any safety margin to deprescribing would be satisfied. And, considering the baseline rate of prescribing was 70%, again, there is basically no possible way a stewardship intervention could fail.

The editorial accompanying this article is darkly amusing, stating “the findings from this study are compelling enough to support CRP testing as an adjunctive measure to guide antibiotic use in patients with acute exacerbations of COPD”. However, it also goes on to note these data hardly identify “which patients (if any) truly benefit from antibiotic therapy”(emphasis mine). Some trials testing 100% antibiotic prescribing vs. zero prescribing (e.g., placebo) have found minimal, or no, benefit. As with procalcitonin, our problem is a pervasive culture of over-prescribing, and ultimate answer is the same for CRP: we don’t need to introduce a marginally informative test into this low-stakes patient population, we simply need to snap out of our collective insanity.

“C-Reactive Protein Testing to Guide Antibiotic Prescribing for COPD Exacerbations”
https://www.nejm.org/doi/10.1056/NEJMoa1803185

Déjà vu: The New Cutting Edge Treatment of Migraines

It’s rimegepant again!

As featured in such posts as … yesterday’s … it’s the same calcitonin gene-related peptide receptor antagonist, but in an entirely separate large, multi-center, double-blind, randomized controlled trial.

And, the results are essentially the same. In this trial, 1,466 participants were randomly assigned to rimegepant or placebo for treatment of a single migraine headache of moderate-to-severe intensity. At two hours post-dose, response rates were 21% with rimegepant and 11% with placebo. Adverse events were similarly rare and generally mild.

Yet again, this tells us rimegepant is better than nothing – and in no way informs us regarding efficacy in their hypothetical patient population: those without response to either over-the-counter therapy or non-responsive/intolerant of the triptans.

Yet again, this study is completely funded by Biohaven Pharmaceuticals, with all the authors employed by and owning stock.

So, the same critiques as yesterday apply – and it’s transparently just another page out of the typical pharmaceutical corporation playbook: do enough to obtain approval, and then let the marketing operation kick into high gear.

“Efficacy, safety, and tolerability of rimegepant orally disintegrating tablet for the acute treatment of migraine: a randomised, phase 3, double-blind, placebo-controlled trial”
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(19)31606-X/fulltext

Addendum: The protocol does have a non-redacted tidbit of a comparison between rimegepant and sumitriptan, based off some unpublished data from a Phase 2b trial. To be taken with a grain of salt, to be sure, but obviously this would not have looked good for rimegepant if any sort of active comparator would have been used:

The New Cutting-Edge Treatment for Migraines

The new sexy business – by which I mean “profitable” – in the treatment of chronic migraine is therapy targeted at the calcitonin gene–related peptide receptor. The past few years have brought several of these to market as ongoing maintenance therapy. This looks at a different application – acute migraine. Their proposed unmet need – the slice of patients for whom various triptans are ineffective.

This is a multi-center, randomized, double-blinded, placebo-controlled trial of rimegepant, an orally-administered CGRP antagonist, administered as a single-dose for acute migraine headache of moderate-to-severe intensity. These authors randomized 1,186 patients in a 1:1 ratio, with the primary end point being freedom from pain at 2 hours after the initial dose.

The winner: rimegepant.

Yes, rimegepant is superior to doing nothing at all for your migraine headache.

And just barely – 19.6% response to rimegepant, compared with 12.0% response to placebo.

The clinical value here is virtually negligible. And, helpfully, the authors provided the primary limitation of this trial for you in the text:

“First, the trial did not include an active comparator to rimegepant.”

The authors note in their introduction many patients receiving triptans do not have a response – 34%! This, however, implies 60+% of patients do have a response – far superior to rimegepant. Then, patients also have an array of over-the-counter options including acetaminophen, ibuprofen, and various caffeine-containing combination therapies. Treating moderate-to-severe migraine attacks with placebo borders on – if not crosses into – unethical territory. Even if this therapy didn’t have a dismal response rate, we still need to generalize it one step further to those who are non-responders to triptans to even have an indication – which would then be the proper enrollment criterion for a trial to ensure the same physiologic features making a patient a triptan non-responder weren’t also a CGPR antagonist non-responder.

Now, no one opposes further exploration of alternative, effective treatments for migraine – headaches, particularly migraine headaches, are relatively common presenting complaints in the Emergency Department. While we have effective abortive treatments for such, there is tremendous value in having a wider array of options for use at home, considering the direct and indirect resource costs and human suffering associated with headaches requiring Emergency Department evaluation and treatment.

But this is junk science – an advertorial in a journal continually proving itself to have virtually no worthy editorial standard:

“Biohaven Pharmaceuticals sponsored the trial, supplied the trial agents, reviewed the trial design, collected the data, and performed data management and analysis. The manuscript was written with the assistance of a medical writer funded by Biohaven Pharmaceuticals. All the authors have confidentiality agreements with Biohaven Pharmaceuticals, either as a condition of employment or in their role as consultants.”

Yet another utter embarrassment for the New England Journal of Medicine.

“Rimegepant, an Oral Calcitonin Gene–Related Peptide Receptor Antagonist, for Migraine”

https://www.nejm.org/doi/full/10.1056/NEJMoa1811090

Addendum: There’s a second study, as well, published in The Lancet with similar results. And, furthermore, deep in a non-redacted part of the protocol, the authors share these unpublished Phase 2b trial results. To be taken with a grain of salt, to be sure, but obviously any comparison with an active drug would have looked much worse for rimegepant:

Pediatric C-Spine Injury Risk Factors

It would seem the Pediatric Emergency Care Applied Research Network (PECARN) is gearing up to develop another decision instrument – this time for cervical spine injuries.

This is a prospective, observational study of 4,091 pediatric blunt trauma patients across four pediatric level-1 trauma centers, surveying treating providers about the presence or absence of factors suspected to be implicated with cervical spine injuries. The factors were selected based on previous studies, as well as those suspected as having potential physiologic plausibility and good interrater reliability. The stated purpose – to ultimately develop a decision instrument akin to their prior work for clinically important minor head injury.

Overall, the prevalence of a cervical spine injury – vertebral fractures, ligamentous injury, intraspinal hemorrhage, or spinal cord injury – was 1.8%. The vast majority of patients in their cohort (78.2%) underwent some sort of imaging, although only 15.8% underwent CT. The most predictive items identified are those already typically considered: diving injuries, axial loading injuries, clotheslining, loss of consciousness (including intubation), neck pain, altered mental status (frequently associated with obvious head injuries), limited range of motion, focal neurologic deficits, and substantial torso and thoracic injuries. Of the 74 patients with CSI in their cohort, effectively only one would have been missed by a decision instrument based on these factors – a fall from 10 feet whose symptoms localized to the thoracic spine, and had a C7 burst with T2-T4 compression fractures. Obviously, this was not missed clinically – again revealing the role of clinical judgment outside of any decision instrument.

The most interesting tidbit, leading into the most substantial implications for generalizability, is their note regarding “high-risk MVC”. They comment previous case-control studies determined both predisposing conditions (e.g., congenital abnormalities of the cervical spine) and high-risk MVC were identified as risk factors, whereas in this study they were not. They discuss the low prevalence in their cohort of those with predisposing conditions, and, conversely, the high prevalence of high-risk mechanisms, to justify their lack of multivariate effect on predicting CSI. Even though they did not fall out as predictive elements in this cohort, a future prediction model intended for general use may yet include such features. As such, these data ought not be fully relied upon to downgrade those potential risk factors.

“Cervical Spine Injury Risk Factors in Children With Blunt Trauma”
https://pediatrics.aappublications.org/content/early/2019/06/18/peds.2018-3221