Friday, February 15, 2013

HIGHLY SENSITIVE CARDIAC TROPONIN ASSAY. HAVE WE GONE TOO FAR?

There is an interesting paper from Norway that is promoting the idea of microscopic evaluation of illnesses. Is that good or bad?







Dr Torbjorn Omland and colleagues from the Arkershus University Hospital, Lorenskog, Norway, published their results from the " Prevention of events with ACE-I therapy ( PEACE ) trial, in the Feb 13th issue of JACC. They randomised 8290 patients with stable CAD ( no UAP episodes in the pass 3 months ), into the group that received Trandolapril and the group with placebo. The follow-up was 5.2 years. Anyway, this study write up subsequently focused on hs cTnI  ( highly sensitive cardiac troponin I ) and hs c TnT ( highly sensitive cardiac troponin T ) assays. They investigators found a high incidence of hs cTnI ( almost 98.5% had hs cTnI of over 1.2 pgm/ml ). This level is at the 99% percentile of the regular c TnI assay. What this means is that many stable CAD patients have an elevated hs c TnI. The investigators also noted that those with elevated hs c TnI had a 34% increase incidence of CV deaths and a 44% increase incidence of admission for heart failure ( and these were patients with normal LV systolic function at baseline ). These of course is after 5.2 years of follow-up.


Herein comes the delima. Should we venture into highly sensitive assays of cardiac troponins, are we over diagnosing an illness that is not there? Afterall, we started by saying that assays in the 99% percentile range are  normal. In fact, there are many conditions that can give a false positive cardiac troponin assay, including other structural heart disease, hypertension, hypertrophic cardiomyopathy, end stage renal disease, etc etc. Yet, if we do not pay cognizance, are we missing out on an important prognostic marker. Should we go ahead and do hs cTnI and find this group of people who are at increase risk of CCF and CV death, what shall we do? At the moment, we have so called marked a disease, for which we do not know what to do. Shall we angiogram this whole lot of stable CAD patients and create more jobs and cost, revascularise them, at even greater cost, or shall we leave them alone, in the knowledge that they may die, and that we do not know what to do with them. Should we re-vascularised them, and I am sure there are many interventionist out there just waiting with their guide catheters and guide wires, are we actually helping them , improve their prognosis or are we just revascularising them for our bread?
Dr Omland, you have now given us a headache.

2 comments:

Winston said...

I understand that there are quite a number of blood tests that can tell if one has a particular medical problem.
Like CD24 blood test for polyps of the colon.
If effective, this would encourage a lot more people to undergo the test rather then doing a colonoscopy which is quite daunting.
Especially the lavage part!
Another aspect of the problem is that some doctors prescribe Fleet lavage to clean the system prior to the colonoscopy.
This lavage is very salty and can cause kidney to the elderly and those with kidney deficiency.

hmatter said...

Hi Winston, I am not so familiar with CD 24 for Ca Colon? I do not know the sensitivity, specificity and predictive value.
I dare say that to the best of my knowledge, the sensitivity, specificity and predictive value of a non-invasive blood test, can never match that of a diagnostic, definitive colonoscopy. Hopeful, it can help to lessen the number of colonoscopy done, which is probably what you mean.