Friday, January 22, 2016

Give More tPA, Pretty Please?

There’s been another scientific update from Genentech-by-proxy, this time lamenting the low utilization for tPA in ischemic stroke patients.  This guideline panel from the AHA notes administering tPA in a safe and timely fashion to stroke patients is a non-trivial organizational exercise, but, what really gets their goat are the various exclusion criteria.  These criteria – minor symptoms, elevated blood pressure, acute trauma, etc. – are aimed at reducing the overall harms of tPA use, but to “help” as many patients as possible, the stroke neurologists believe it is necessary to break all the eggs.

This document, most prominently, is an entertaining exercise in linguistic calisthenics.  Clearly, these authors would like to treat as many patients as possible with tPA.  In their pursuit of these justifications, absent evidence, they torture the English language into providing he most diverse possible assortment of non-committal positivity.  To wit:
  • “There should be no exclusion …”
  • “Intravenous alteplase treatment is reasonable …”
  • “Intravenous alteplase administration for ischemic stroke may be considered …”
  • “…  it is reasonable that urgent intravenous alteplase treatment not be delayed …”
  • “Intravenous alteplase may be considered on a case-by-case basis.”
  • “Intravenous alteplase may be reasonable …”
  • “Use of intravenous alteplase in carefully selected patients … may be considered …”
  • “In acute ischemic stroke patients … intravenous alteplase may be carefully considered …”
  • “… administration of intravenous alteplase is reasonable and probably recommended …
  • “Intravenous alteplase treatment is probably recommended …”
  • “Patients … may benefit from intravenous alteplase …”
  • “… intravenous alteplase treatment appears safe and may be beneficial …”
  • “… intravenous alteplase may be as effective … and may be a reasonable option …”
  • “Intravenous alteplase is probably indicated …”
I.e., this scientific update may be a reasonably probably carefully considered option.  Or, as I've heard Jerry Hoffman say, each instance of the word "may" should be paired with its logical partner – "may not" – for the appropriately even-handed reading.

Other gems:
The risk of symptomatic intracranial hemorrhage in the SM population is quite low; thus, starting intravenous alteplase is probably recommended in pref- erence over delaying treatment to pursue additional diagnostic studies (Class IIa; Level of Evidence B).
The authors devote half a page to overstating the safety margin of tPA in stroke mimics by focusing on a single 100-patient cohort.  The clinical anecdotes of the two patient suffering sICH, and being lucky enough to survive, in this cohort are provided as apparently definitive reassurance.

And:
For patients with mild but disabling stroke symptoms, intravenous alteplase is indicated within 3 hours from symptom onset of ischemic stroke. There should be no exclusion for patients with mild but nonetheless disabling stroke symptoms in the opinion of the treating physician from treatment with intravenous alteplase because there is proven clinical benefit for those patients (Class I; Level of Evidence A).
The pursuit of treating mild, but nonetheless disability symptoms is not new – and not specifically offensive.  However, they give this recommendation “Class I, Level of Evidence A”, which is the strongest level of support, based on, apparently, multiple randomized clinical trials or meta-analyses.  Except, however, their justification in the text for this recommendation is merely:
Alteplase may be beneficial for milder stroke cases judged as potentially disabling despite low NIHSS scores. The NINDS trialists explored 5 different definitions of minor stroke in a post hoc analysis and found benefit for alteplase across all definitions. However, data are not available on the effect of alteplase for milder stroke cases judged as not potentially disabling at presentation. Because nearly 3000 such cases of ischemic stroke were excluded from the 2 NINDS trials for mild symptoms, any analysis of mild symptoms within the 2 NINDS trials is difficult to interpret.
Why let the true level of evidence affect the final recommendation categorization?

If left to my own devices, this post could meander onward for an eternity.  I will, then, now step aside to allow the motivated reader to move along to source document itself.

“Scientific Rationale for the Inclusion and Exclusion Criteria for Intravenous Alteplase in Acute Ischemic Stroke”
http://stroke.ahajournals.org/content/early/2015/12/22/STR.0000000000000086.abstract

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