Using CTA to Predict tPA Failures

tPA, the “proven” therapy foisted inappropriately on Emergency Medicine and our patients, doesn’t work.

Rather – as I’ve said before – it simply doesn’t work the way we’ve been taught.

The core concepts of the theoretical utility of tPA for ischemic stroke are demonstrated nicely in the new endovascular trials.  Patients do well, better than the natural course of their disease if:

  • There is significant viable brain distal to the vascular occlusion as a result of collateral circulation.
  • The vessel is rapidly and reliably opened.

Both these criteria were met in the new endovascular trials, requiring imaging evidence of a small infarct core and use of modern retrieval devices.  However, the broad population being pushed as candidates for tPA are not as fortunate – the key feature being the abysmal recanalization rate of tPA, only 46% in a meta-analysis of tiny case series from mostly the ‘90s.  Comparatively, in the same report, early spontaneous recanalization was present in 24%.  So, obviously, there’s only even a 1 in 5 chance a patient will receive an additive benefit from tPA for recanalization – which, with some heterogeneity, means our NNT has a maximum upper bound if we treat an unselected population of all-comers.

This study is a small case series from the ongoing PRove-IT study, looking specifically at, essentially, the permeability of intracranial thrombi.  These authors hypothesized this might be an important predictor of recanalization because, after all, if there’s no flow through an impermeable occlusion, tPA can never fully contact the substrate of interest.  These authors used CT angiography to estimate occult anterograde flow versus retrograde flow, and followed-up recanalization following tPA.

There are only 66 patients in this small observational study, but the results are rather compelling.  They estimated 17 (25.8%) of patients had some minimal anterograde flow through the occluded vessel.  These patients, with some detectable flow, had a 66.7% recanalization rate.  Conversely, the 49 patients without any residual anterograde flow had a recanalization rate of only 29.7% – a rate not dissimilar to spontaneous.  And, outcomes followed recanalization – logically, considering detectable anterograde flow and effective destruction of the occlusion are highly favorable features.

The moral of the story?  It’s quite clear there are promising venues for determining which patients have the best chance to benefit from tPA – and those for whom the harms exceed those chances.  The perpetual “tPA for all!” call being added to guidelines and quality measures is a product of conflict-of-interest and corporate sponsorship, not good medicine – and we can do better, if we simply cared to investigate.

“Occult Anterograde Flow Is an Under-Recognized But Crucial Predictor of Early Recanalization With Intravenous Tissue-Type Plasminogen Activator”
http://www.ncbi.nlm.nih.gov/pubmed/25700286

The Case of the Bloody Lumbar Punctures

Modern evaluation for aneurysmal subarachnoid hermorrhage, with some debate, may include definitive non-contrast CT performed within six hours of symptom onset.  The traditional evaluation, and still recommended beyond six hours, involves a lumbar puncture, looking for red blood cells or xanthrochromia.

This latest tale of woe from Jeff Perry’s SAH data details the pragmatic effectiveness of the traditional pathway, focusing on the primary confounder: traumatic taps.  They report on 1,739 patients undergoing lumbar puncture as part of this evaluation, and, unfortunately, the numbers are grim:  641 (36.8%) samples were abnormal in the final tube of CSF collected.  However, it isn’t so bad – 476 of those had fewer than 100 RBCs x 10^6/L, with many having only a handful of cells.  But, still, that leaves 165 patients with fairly substantial numbers of RBCs in their CSF.

Because, all told, only 15 received a final diagnosis of aneurysmal SAH.

Why is this so grim?  Because 419 of these 626 patients with RBCs on their LP subsequently were subjected to angiography – with 404 of them negative.

And xanthrochromia?  Some predictive value – 7 of 15 patients diagnosed with SAH displayed xanthrochromia, but, obviously there were 8 patients with SAH who did not, along with 16 instances of xanthrochromia in patients without SAH.

The final gist of the paper is to generate a 100% sensitive cut-off to exclude SAH – for which the authors choose 2000 x 10^6 and absent xanthrochromia.  This results in a specificity of 91.2% and a positive LR or 11.4.  This is a pretty good positive LR, but, unfortunately, given such a vanishingly rare disease, the PPV was only 21.4% in their cohort.

However, one major flaw in this study is it doesn’t usefully describe the population of true interest to Emergency Physicians – the test characteristics of those with a negative CT and a positive LP.  There were 77 patients who did not undergo CT prior to LP, but, more importantly, 10 of the patients included in this cohort had visible SAH on CT recognized by the staff radiologist, but not the Emergency Physician.  Therefore, if you practice in a setting without neuroradiology coverage, this is generalizable.  Otherwise, we can exclude those 10 cases and boggle at the massive resource utilization in terms of LPs and angiography in order to pick up just 5 cases of occult aneurysmal SAH.

In patient-oriented terms – based on these data – the risk of SAH after a negative CT performed greater than 6 hours after onset is about 1 in 330.  Using their cut-off of 2000 x10^6, the chance of a true positive LP is about 1 in 12.  A vast improvement, to be sure, but probably still not a pathway very many patients are going to choose when presented with these odds.

“Differentiation between traumatic tap and aneurysmal subarachnoid hemorrhage: prospective cohort study”
http://www.ncbi.nlm.nih.gov/pubmed/25694274 (free fulltext)

Rampant Underreported Research Misconduct

It is not surprising to hear clinical trials sometimes struggle with data integrity and quality issues.  Such undertakings can be logistically challenging, and certainly any substantial scope of effort leads to the occasional cutting of corners.

However, there are also millions (or billions) of dollars in revenue, along with multiple professional reputations, at stake.  This creates fertile territory for the more nefarious sort of data corruption.  In some instances, the Food and Drug Administration performs site monitoring as evaluation for misconduct.  And, as this study indicates, the FDA sometimes discovers serious issues – issues almost always swept under the rug.

Using a variety of methods, including Freedom of Information Act requests, FDA.gov site exploration, and other FDA published warnings, these authors compiled a list of 421 serious irregularities identified by FDA audit.  However, heavily redacted language in many of the documents discovered precluded linkage to clinical trials – resulting in only 57 published trials that could be linked to serious violations.  These 57 trials resulted in 78 identifiable publications – only 3 of which mentioned or addressed the issues raised by the FDA.  Those three specifically noted data excluded due to protocol errors, data falsification, or inappropriate monitoring.  The remaining 75 publications did not.

A couple examples:
  • 8 of 16 FDA inspections of sites for RECORD 4, a rivaroxaban trial for DVT prophylaxis, identified unblinding, falsification of records, and randomization improprieties.  The associated study publications do not mention such issues.
  • A clinical site in China falsified data regarding apixiban in ARISTOTLE.  Excluding such data from the final study report would eliminate any apparent mortality benefit, but publications continue reporting mortality benefit analyses based on the entire data set.
The lack of transparency and apparent action regarding what is certainly just the tip of the iceberg is staggering.  How is it our own drug safety organization fails to protect patients on such a scale?  Is it any wonder so few clinical trial results hold up on re-examination?

“Research Misconduct Identified by the US Food and Drug Administration”
http://www.ncbi.nlm.nih.gov/pubmed/25664866

Sore Throats More Dangerous than Terrorists

1 in 5 Sore Throats Tied to Scary Bacteria, Study Finds

Thanks, HealthDay.

Now, clickbait headlines aside, what on earth are they referring to?  And, if ~50% of acute pharyngitis already receives inappropriate antibiotics – how can this sort of news release help us maintain any sort of reasonable antibiotic stewardship while also cultivating some modicum of Press Ganey approval?

This is a cross-sectional survey of throat swabs performed on a convenience sample of students at the University of Alabama.  PCR for an expanded cohort of bacterial pathogens was performed on 312 patients presenting to the student health center with acute pharyngitis, and compared with 180 asymptomatic volunteers.  Among symptomatic patients, 20.5% of PCR detected Fusobacterium necrophorum, compared with 9.4% of the asymptomatic cohort, leading to such conclusions as: “approximately 11% of cases of pharyngitis in patients coming to this university health clinic were caused by F. necrophorum.”  Group A Streptococcus, by comparison, was detected in only 10.3% of symptomatic patients and 1.1% of asymptomatic.

So, an epidemic of F. necrophorum?  Should we, as these authors suggest, be considering penicillin for all sore throats – based on the feared complication of Lemierre syndrome – regardless of rapid streptococcal antigen testing?

No.

While, we shouldn’t forget about F. necrophorum, particularly in the adolescent/young adult population, it is important to remember the vast majority of pharyngitis – even bacterial – is self-limited, with minimal benefit from antibiotics, either for symptom relief or suppurative complications.  For Group A Streptococcus, it is reasonable to suggest well over 200 cases must be treated with antibiotics to prevent progressive disease, and rheumatic fever is virtually extinct.  However, we have no similarly useful statistics regarding F. necrophorum – mostly because serious downstream complications are so rare they are still literally one-in-a-million case reports.  Symptomatic management and judicious treatment for acute pharyngitis remains the most appropriate strategy, despite the prevalence of this “scary bacteria”.

“The Clinical Presentation of Fusobacterium-Positive and Streptococcal-Positive Pharyngitis in a University Health Clinic”
http://www.ncbi.nlm.nih.gov/pubmed/25686164

Distorted Treatment Effects for Steroids for Pneumonia

This is the second “steroids for pneumonia” trial published in the last few weeks.  The last trial, enrolling 785 patients with community-acquired pneumonia, showed a small – but potentially relevant – reduction in inpatient length-of-stay.  No differences were noted with respect to mortality or treatment failure.

This trial, however, is a bit different.  In an effort to maximize the theoretical mortality reduction associated with steroid use in pneumonia, these authors targeted therapy specifically at those in the highest pneumonia severity risk categories and required a CRP >150 mg/L.  Patients were then randomized to 0.5 mg/kg twice daily of intravenous methylprednisolone or placebo.  The primary outcome was “treatment failure”, which was composed of two definitions – one specifically for early deterioration and one for late deterioration.

At face value – the results are excellent.  There was 31% failure rate in the 59 patients in the placebo group, compared with 13% of the 61 patients in the methylprednisolone group.  Deaths were 10% in the methylprednisolone group and 15% for placebo, and few adverse events occurred in either group – these differences, however, did not reach statistical significance due to the small sample size.

But this trial is essentially noise, full of baseline confounders and inconsistencies.  To start, simply, note each center enrolled, on average, one patient every-other month for eight years – only managing to screen 519 total patients with pneumonia for eligibility over the course of the trial.  This does not reflect a well-executed trial infrastructure.  An excess of 11% of placebo patients were admitted to the ICU, reflecting in part a 20% excess of placebo patients with shock as part of their initial presentation.  Shock and multiple organ failure was the major cause of death in the placebo group, compared with disease progression in the steroid cohort.

Furthermore, 40% of the placebo patients presenting with shock did not receive antibiotics within 4 hours of arrival.  Causative organisms were detected for 51% of the steroid cohort, compared with 30% of the placebo group – with 21% of the steroid cohort having a “respiratory virus” compared with 8% in the placebo group.  Antibiotic use was also odd, with the prevailing choice being ceftriaxone plus levofloxacin, rather than the typical ceftriaxone + azithromycin combination used for CAP.

How this managed to get published in one of the supposedly pre-eminent medicine journals is beyond me.  With only 120 patients, all the substantial absolute differences in baseline characteristics and care heavily distort the overall results.  Mostly, unfortunately, it looks like placebo patients were sicker and received less-adequate initial care – and everything measured in this small trial is suspect as a result.

“Effect of Corticosteroids on Treatment Failure Among Hospitalized Patients With Severe Community-Acquired Pneumonia and High Inflammatory Response”
http://www.ncbi.nlm.nih.gov/pubmed/25688779

Irresponsible Use of NOACs in End-Stage Renal Disease

Frequent readers may have noted this blog is somewhat skeptical regarding the novel oral anticoagulants, with particular criticism reserved for dabigatran.*  The bleeding risks, particularly for dabigatran, are profoundly increased in renal impairment – while the Factor Xa inhibitors simply do not have sufficient safety data to describe their risks in this population.

So, in dialysis patients with zero renal function – wouldn’t it perhaps be safest to continue using our present, time-tested, warfarin anticoagulation strategy?

This review of the Fresenius Medical Care database of end-stage renal patients on dialysis captured 8,064 patients with non-valvular atrial fibrillation who were initiated on anticoagulation between 2010 and 2014.  During this time, 5.9% of patients receiving new anticoagulation were initiated on dabigatran or rivaroxaban, with the remainder started on warfarin or aspirin.  And, dabigatran or rivaroxaban use increased the incidence of minor bleeding, major bleeding, and bleeding-associated mortality – with relative risk increases ranging from ~1.3 for minor bleeding to ~1.7 for hemorrhagic death.  Even rates for ischemic stroke were low in all groups, and no meaningful protective difference for thromboembolic events was observed.  Small baseline differences between the various anticoagulant cohorts are present, but they are probably clinically unimportant.

More bleeding?  More death?  It seems clear it is not responsible medicine to initiate the NOACs in a dialysis population.

“Dabigatran and Rivaroxaban Use in Atrial Fibrillation Patients on Hemodialysis”
http://www.ncbi.nlm.nih.gov/pubmed/25595139

*Disclosure: I provided legal consultation pertaining to dabigatran, with funds paid to my institution.