Normal Isn't Necessarily Optimal

Rather than make home visits yesterday, I substituted for another doc and worked in the UNLV Student Health Center.  It certainly makes for a nice change of pace, as I don't typically have a chance to provide counsel regarding hormonal contraception and prevention of sexually transmitted diseases.  However, I stopped dead in my tracks when a kid, a teen really, showed up for a pre-employment physical and pointed out his medical and family history: polycythemia vera!

It turns out that a randomized controlled trial was published early online this weekend in NEJM in which the authors concluded that a hematocrit goal of <45% was associated w/lower of risk of cardiovascular death or thrombotic events in patients avg 65yo w/polycythemia compared to a goal of 45-50%. In essence, 365 patients w/polycythemia vera were followed for an average of 31 months after randomization to either of the two stated goals.  Normal reference range for hematocrit goes up to 51% or so depending upon the lab, so it's interesting to note that normal isn't necessarily optimal!

So of course I had to ask him what was his goal hematocrit?  The answer?  45-46% which would place him at higher risk for untoward events if he were in a similar demographic (notice the age differential).  Still forewarned is forearmed so I emailed him the abstract to the study and asked him to review its applicability w/his hematologist.

In an analogous situation, testosterone is known to stimulate bone marrow production leading to secondary polycythemia.  This is usually due to supraphysiologic levels so I always recommend smaller more frequent doses for those who take injectable testosterone.  But if the hematocrit still runs high despite my best attempts to smooth out the peak & trough, I then recommend therapeutic phlebotomy to minimize this same risk of cardiovascular death & thrombotic events.  Granted this study was performed on a population of patients w/PV, but it does make me wonder about its generalizability to secondary polycythemia.  

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