The JAK2^V617F Mutation in Blood Donors with High Haematocrit.

By the introduction for routine tests of automated counters it has become easy and extremely common the finding of abnormal or near normal laboratory results. During blood donations haematocrit (Htc) and haemoglobin level (Hb) are regularly tested to avoid a blood donation in the case of anaemia as this is the most frequent cause of exclusion from the donation. However it is not rare to observe a level of Hb or Htc upper or close the normal highest limit. Starting from the 1^st of January 2006 to the 31^st December 2006, we have collected 11240 donations in total from 5636 regular blood donors (total donation index 1.99) and selected on the basis of Htc, limit upper 50% for man and 46% for women, 84 males and 19 females. In this cohort, during a 1846 years donation period, the average of donations for males was 22.2 while for females was 11.4. We collected randomly and used as control group 79 donors (59 males and 20 females) with normal Htc levels in the last blood donation. For the identification of the V617F (1848 G>T) mutation within JAK2 we used the method published by Jones ed al. in 2005 named amplification refractory mutation system (ARMS). Among the 84 men with high haematocrit level we have been able to identify 1 blood donor positive for this mutation. This blood donor had Htc equal to 50.6 in the last donation, while the average Htc in the last year was 51.7. These results account for a total prevalence of the JAK2 mutation in 1% of the blood donor population with elevated Ht (1 out of 103) while it is 0.6% (1 out of 183) of the entire population of blood donors in this study or 0.02% of the entire cohort appertaining to our transfusion service. Our results seem also in keeping with the few studies evaluating blood donors (Zanella et al., Transfusion 1987) or normal population (Ruggeri et al., Ann Int Med 2003). In both these studies the prevalence of MPD was around 3% which is not so far away from that found in our cohort (asymptomatic patients) but much higher than that supposed in hospital based cohorts in previous studies (100 fold increased). The hypothesis that the prolonged myeloid stimulus from phlebotomies can induce inhibition of the feed-back control as well as blood donations triggered the onset of a pre-existing latent primary myeloproliferative disease needs further studies to be confirmed.