Non-Association of Methylenetetrahydrofolate Reductase (MTHFR) Polymorphisms with Homocysteine Levels, Venous or Arterial Thromboses in 1,141 North-Central Appalachian Patients

Abstract

Objectives : MTHFR polymorphism testing has been used by clinicians for thrombophilia risk assessment. We questioned the utility of such testing. Methods : 1,141 patients age 18 and above had MTHFR testing for both C677T and A1298C polymorphisms, 2006 through 2012. Available plasma homocysteine levels were obtained and ICD-9 billing codes were grouped to identify venous or arterial clots in these patients. Results : 901 women and 240 men were tested; median age in women was 33 years (range 18-86); median age in men was 47 years (range 18-83). County of residence mapping confirmed that this MTHFR tested population was from north-central Appalachia. Only 144 (13%) of the 1,141 patients had no polymorphism at either the C677T or the A1298C locus; only 4 patients (0.4%) had 3 or more polymorphisms; 993 patients (87%) had either one or two polymorphisms. We found polymorphism frequency pattern similar in both sexes. Although men had higher homocysteine levels, MTHFR polymorphisms did not associate with homocysteine levels in either sex. In 901 women tested, the ICD-9 coded incidence of arterial clots was 20%, and of venous clots was 21%; in 240 men tested, the incidence of arterial clots was 48% and of venous clots was 40%. MTHFR polymorphisms did not associate with arterial or venous clots in either sex. Based on CPT billing codes, a minimal cost estimate was $137,000 for performing these 1,141 MTHFR tests. Conclusions : MTHFR testing was costly and did not add useful information during thrombophilia evaluation in this patient population.