Topics:
factor v leiden, venous thromboembolism

In a previous article,1  we reported population-based findings from the Longitudinal Investigation of Thromboembolism Etiology (LITE) on factor V Leiden and risk of venous thromboembolism (VTE). We used a nested case-control design (301 new VTE cases and 630 controls through 1998) from the prospective Atherosclerosis Risk in Communities (ARIC) Study and Cardiovascular Health Study (CHS). The odds ratio, overall, for risk of VTE for carriers of factor V Leiden was 3.67 (95% CI, 2.20-6.12).1 

We recently extended LITE to additional cases and controls through 2002. In the process, we discovered and corrected an error in the original selection of controls for ARIC that had caused us to oversample participants who had died into the control group for our earlier report. Compared with our published report, the updated sample of 502 cases and 1021 controls yielded an almost identical odds ratio for factor V Leiden of 3.46 (95% CI, 2.20-5.43). Genotype distributions and other odds ratios for factor V Leiden (Tables 1–2) are also similar to those in our original report's Tables 1–2.1  The estimate for African Americans remains quite imprecise from this large prospective study because of the infrequency of factor V Leiden in African Americans.

Table 1

Frequency of factor V Leiden in VTE cases and controls, LITE

Factor V Leiden
Genotyped, no.Wild type, no.Heterozygous, no.Homozygous, no.Hetero- or homozygous, %
Cases 502 450 48 4 10.3 
    White 368 319 45 4 13.3 
    African American 134 131 3 0 2.2 
Controls 1021 988 33 0 3.2 
    White 751 719 32 0 4.2 
    African American 270 269 1 0 0.4 
Factor V Leiden
Genotyped, no.Wild type, no.Heterozygous, no.Homozygous, no.Hetero- or homozygous, %
Cases 502 450 48 4 10.3 
    White 368 319 45 4 13.3 
    African American 134 131 3 0 2.2 
Controls 1021 988 33 0 3.2 
    White 751 719 32 0 4.2 
    African American 270 269 1 0 0.4 
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Table 2

Age-adjusted odds ratio and 95% CI for VTE in relation to factor V Leiden, 1987-2002, LITE

SubgroupNo. casesOR95% CI
Overall 502 3.46 2.20-5.43 
Whites 368 3.45 2.17-5.49 
African Americans 134 6.26 0.64-60.8 
ARIC 312 4.56 2.55-8.15 
CHS 190 2.16 1.03-4.51 
Incident 443 3.14 1.96-5.02 
Recurrent 59 5.90 2.73-12.7 
Idiopathic 216 5.78 3.50-9.55 
Secondary 286 1.89 1.04-3.45 
DVT 418 3.79 2.39-6.01 
PE 153 2.81 1.44-5.46 
Both 69 3.93 1.74-8.88 
SubgroupNo. casesOR95% CI
Overall 502 3.46 2.20-5.43 
Whites 368 3.45 2.17-5.49 
African Americans 134 6.26 0.64-60.8 
ARIC 312 4.56 2.55-8.15 
CHS 190 2.16 1.03-4.51 
Incident 443 3.14 1.96-5.02 
Recurrent 59 5.90 2.73-12.7 
Idiopathic 216 5.78 3.50-9.55 
Secondary 286 1.89 1.04-3.45 
DVT 418 3.79 2.39-6.01 
PE 153 2.81 1.44-5.46 
Both 69 3.93 1.74-8.88 

DVT indicates deep vein thrombosis; PE, pulmonary embolism.

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We were unable to repeat other measures in our original report1  (activated protein C resistance, factor V concentration, and HRZ haplotype) to confirm no influence of the control selection error. Nevertheless, these factor V Leiden results offer confidence of the accuracy of our original report.1 

Correspondence: Aaron R. Folsom, University of Minnesota, School of Public Health, 1300 South Second St, Ste 300, Minneapolis, MN 55454-1015; e-mail: folsom@epi.umn.edu.

1
Folsom AR, Cushman M, Tsai MY, et al. A prospective study of venous thromboembolism in relation to factor V Leiden and related factors.
Blood
2002
;
99
:
2720
–2725.
Copyright © 2007 by The American Society of Hematology
2007
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