Factor V Leiden (Activated Protein C Resistance) Versus Factor V Deficiency in Padua, Italy

Abstract

Ten homozygous patients with factor V deficiency and 19 homozygous patients with activated protein C (APC) resistance were seen in Padua during the last 30 or 3 years, respectively. The actual numbers of heterozygous patients seen during the same periods of time were 41 and 306, respectively. All patients came from the northeastern part of Italy with a population of 10,000,000 people. The probable prevalence of homozygous patients was obtained by multiplying the actual number by four. The theoretical prevalence of heterozygous patients was obtained using the formula 2 qp, where q is the frequency of the abnormal gene as calculated by the square root of frequency of the homozygotes and p is the frequency of the normal allele as calculated by the formula p = (1 - q). Using such calculations, the number of heterozygotes probably exist ing in northeastern Italy is 39,840 and 56,497, respectively for the factor V deficiency and for APC resistance. After correction for the different observation periods (3 years vs. 30 years), there are 56,497 per 10 million people (5.6% of the population) for factor V Leiden. The prevalence of factor V deficiency is 0.39% of the population. Therefore the factor V Leiden muta tion responsible for APC resistance appears to be more preva lent than factor V deficiency on the basis of actual figures and accepted theoretical calculations.