Thursday, December 29, 2011

Yet Another Highly Sensitive Troponin - In JAMA

...peddling the same tired phenomenon of magical thinking regarding the diagnostic miracle of highly sensitive troponins.  However, this one is different because it's been picked up by the AP, CBS News, Forbes, etc. saying: "Doctors are buzzing over a new blood test that might rule out a heart attack earlier than ever before" and other such insanity.  Yes, our hearts are in atrial flutter around the water cooler about a new assay that changes sensitivity from 79.4% to 82.3% at hour 0 and 94.0% to 98.2% at hour 3.


Unless you actually read the article.

Somehow, contrary to every other high-sensitivity troponin study, this particular highly-sensitive troponin had increased specificity as well - which simply doesn't make sense.  If you're testing for the presence of the exact same myocardial strain/necrosis byproduct as a conventional assay, it is absolutely inevitable that you will detect a greater number of >99th percentile values in situations not reflective of acute coronary syndrome.  The only way to increase both sensitivity and specificity is to measure something entirely different.

Or, if it suits your study aims, you can manipulate the outcomes on the back end.  In this study, the final diagnosis of ACS "was adjudicated by 2 independent cardiologists" whose diagnostic acumen is enhanced by financial support including Brahms AG, Abbott Diagnostics, St Jude Medical, Actavis, Terumo, AstraZeneca, Novartis, Sanofi-Aventis, Roche Diagnostics, and Siemens.

I am additionally not impressed by their results reporting - sensitivity and specificity, followed by the irrelevant positive predictive and negative predictive values.  Since the PPV and NPV are determined by the incidence of disease in their cohort, they're giving us numbers that are potentially not externally valid.  Rather, they should be reporting positive and negative likelihood or odds ratios - which are relatively cognitively unwieldy, but at least not misleading, but conceptually facile, like PPV and NPV.

And this is from JAMA.  Oi.

"Serial Changes in Highly Sensitive Troponin I Assay and Early Diagnosis of Myocardial Infarction"

No comments:

Post a Comment

Comments on posts > 10 days old will be moderated; blame spammers.