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From www.bloodjournal.org by guest on June 12, 2017. For personal use only. 2091 CORRESPONDENCE Detection of the Factor V Leiden Mutation in a Nonselected Black Population To the Editor: The factor V Leiden mutation was first described in 1994.' The mutation replaces Arg 506 of factor V with Gln, and alters the cleavage site on the activated molecule (factor Va), which is critical for the action of activated protein C (APC). As a result, factor Va derived from the mutant sequence is resistant to the anticoagulant effect of APC. Studies have shown a statistically significant increase in the risk of clinical venous thromboembolism amoung patients homozygous and heterozygous for factor V Leiden.2-4 Previous studies of the incidence of clinical A X resistance and the factor V Leiden mutation have focused primarily on white populations, where the prevalence has been reported variously as 2% to 5%.'.5.6 This mutation has been demonstrated in at least one African-American individual with clinical th"bosis,2 but we have found no information on the prevalence of factor V Leiden within the American black population. It has been predicted by some that the abnormality might be found predominantly in individuals of European extraction. We have investigated the incidence of the factor V Leiden mutation in black inpatients and outpatients in our hospital setting, and have found, surprisingly, that the incidence of this mutation in the black population is not significantly different f " that in whites. Randomly selected blood samples were obtained from the YaleNew Haven Hospital hematology laboratory and the ethnic background of the patients was determined from hospital records. Once ethnic background was recorded, the samples were numbered consecutively and stored anonymously. In addition, we studied stored DNA samples from black individuals already available in the laboratory from previous population studies. Genomic DNA was isolated and analyzed by polymerase chain reaction and digestion of the APC cleavage site using previously described methods.' The factor V Leiden mutation destroys an Mnl-1 restriction enzyme site, giving characteristic restriction fragment length polymorphism (RFLP) patterns for heterozygotes and homozygotes. Results were obtained for 214 black individuals, of whom 3 (1.4%) were heterozygous for the factor V Leiden mutation. By comparison, the incidence of the mutation in a group of 126 white patients selected in the same manner was 2 (1.6%). yielding a relative risk of 0.88 (Fisher Exact two-tailed test, P = 1.0000, 95% confidence interval 0.12 to 7.64). These data do not support the hypothesis of a difference between the incidence of the factor V Leiden mutation in the black and white populations studied. Although the possibility of the introduction of an ancestral Caucasian gene into the black population cannot be ruled out, these results strongly suggest multiple mutational events giving rise to the factor V Leiden genotype. Paul Pottinger Fridbjom Sigurdsson Nancy Berliner Section of Hematology Department of Intemal Medicine Yale University School of Medicine New Haven, CT REFERENCES 1. Bertina RM, Koeleman BP, Koster T, Rosendaal FR, Dirven RI,de Ronde H, van der Velden PA, Reltsma PH: Mutation in blood coagulation factor V associated with resistance to activated protein C. Nature 369:64, 1994 2. Greengard JS, Sun X, Xu X, Fernandez JA, Griffin JH, Evatt B: Activated protein C resistance caused by Arg506Gln mutation in factor Va. Lancet 343:1362, 1994 3. Zoller B, Dahlback B: Linkage between inherited resistance to activated protein C and factor V mutation in venous thrombosis. Lancet 343:1536, 1994 4. Voorberg J, Roesle J, Koopman R, Buller H, Berends F, ten Cate JW, Mertens K, van Mourik JA: Association of idiopathic venous thromboembolism with a single point mutation at Arg 506 of factor V. Lancet 343:1535, 1994 5 . Svensson PJ, Dahlback B: Resistance to activated protein C as a basis for venous throbosis. N Engl J Med 330517, 1994 6. Koster T, Rosendaal FR, de Ronde F, Briet E, Vandenbroucke JP, Bertina RM: Venous thrombosis due to poor anticoagulant response to activated protein C: Leiden thrombophilia study. Lancet 342:1503, 1993 From www.bloodjournal.org by guest on June 12, 2017. For personal use only. 1996 87: 2091 Detection of the factor V Leiden mutation in a nonselected black population [letter] P Pottinger, F Sigurdsson and N Berliner Updated information and services can be found at: http://www.bloodjournal.org/content/87/5/2091.citation.full.html Articles on similar topics can be found in the following Blood collections Information about reproducing this article in parts or in its entirety may be found online at: http://www.bloodjournal.org/site/misc/rights.xhtml#repub_requests Information about ordering reprints may be found online at: http://www.bloodjournal.org/site/misc/rights.xhtml#reprints Information about subscriptions and ASH membership may be found online at: http://www.bloodjournal.org/site/subscriptions/index.xhtml Blood (print ISSN 0006-4971, online ISSN 1528-0020), is published weekly by the American Society of Hematology, 2021 L St, NW, Suite 900, Washington DC 20036. 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