VTE in relatives according to if the index case had factor V Leiden or the prothrombin 20210A gene variant
| Findings in relatives . | Total . | No FVL and no PGM in index cases . | Any FVL or PGM in index cases . |
|---|---|---|---|
| Index cases had provoked VTE, n | 865 | 742 | 123 |
| Person-years of observation, n | 36 511 | 31 475 | 5 036 |
| Previous VTE, n | 21* | 19 | 2 |
| Incidence per 100 person-years (95% CI) | 0.06 (0.04-0.09) | 0.06 (0.04-0.09) | 0.04 (0.01-0.15) |
| Unadjusted odds ratio (95% CI) | — | Reference | 0.63 (0.15-2.74) |
| Adjusted odds ratio (95% CI)† | — | Reference | 0.61(0.14-2.66) |
| Index cases had unprovoked VTE, n | 1 752 | 1 250 | 502 |
| Person-years of observation, n | 68 066 | 48 866 | 19 200 |
| Previous VTE, n | 102‡ | 62 | 40 |
| Incidence per 100 person-years (95% CI) | 0.15 (0.12-0.18) | 0.13 (0.10–0.16) | 0.21 (0.15-0.28) |
| Unadjusted odds ratio (95% CI) | — | Reference | 1.68 (1.09-2.59) |
| Adjusted odds ratio (95% CI)† | — | Reference | 1.48 (0.94-2.33) |
| All index cases, n | 2 617 | 1 992 | 625 |
| Person-years of observation, n | 104 577 | 80 341 | 24 236 |
| Previous VTE, n | 123 | 81 | 42 |
| Incidence per 100 person-years (95% CI) | 0.12 (0.10-0.14) | 0.10 (0.08-0.12) | 0.17 (0.13-0.23) |
| Unadjusted odds ratio (95% CI) | — | Reference | 1.70 (1.16-2.50) |
| Adjusted odds ratio (95% CI)† | — | Reference | 1.34 (0.89-2.01) |
| Findings in relatives . | Total . | No FVL and no PGM in index cases . | Any FVL or PGM in index cases . |
|---|---|---|---|
| Index cases had provoked VTE, n | 865 | 742 | 123 |
| Person-years of observation, n | 36 511 | 31 475 | 5 036 |
| Previous VTE, n | 21* | 19 | 2 |
| Incidence per 100 person-years (95% CI) | 0.06 (0.04-0.09) | 0.06 (0.04-0.09) | 0.04 (0.01-0.15) |
| Unadjusted odds ratio (95% CI) | — | Reference | 0.63 (0.15-2.74) |
| Adjusted odds ratio (95% CI)† | — | Reference | 0.61(0.14-2.66) |
| Index cases had unprovoked VTE, n | 1 752 | 1 250 | 502 |
| Person-years of observation, n | 68 066 | 48 866 | 19 200 |
| Previous VTE, n | 102‡ | 62 | 40 |
| Incidence per 100 person-years (95% CI) | 0.15 (0.12-0.18) | 0.13 (0.10–0.16) | 0.21 (0.15-0.28) |
| Unadjusted odds ratio (95% CI) | — | Reference | 1.68 (1.09-2.59) |
| Adjusted odds ratio (95% CI)† | — | Reference | 1.48 (0.94-2.33) |
| All index cases, n | 2 617 | 1 992 | 625 |
| Person-years of observation, n | 104 577 | 80 341 | 24 236 |
| Previous VTE, n | 123 | 81 | 42 |
| Incidence per 100 person-years (95% CI) | 0.12 (0.10-0.14) | 0.10 (0.08-0.12) | 0.17 (0.13-0.23) |
| Unadjusted odds ratio (95% CI) | — | Reference | 1.70 (1.16-2.50) |
| Adjusted odds ratio (95% CI)† | — | Reference | 1.34 (0.89-2.01) |
CI, confidence interval; FVL, factor V Leiden; PGM, prothrombin 20210A gene variant; VTE, venous thromboembolism.
Of the 21 episodes of VTE in first-degree relatives of index cases with provoked VTE, 2 were unprovoked, 3 were associated with cancer, 9 were provoked by major reversible risk factors, 0 were provoked by minor reversible risk factors, and risk factors were uncertain in 7.
Adjusted for intrafamily clustering, age of index cases, age of first-degree relatives during the period of observation, sex of first-degree relatives, and whether the first-degree relatives were dead or alive at enrolment.
Of the 102 episodes of VTE in first-degree relatives of index cases with unprovoked VTE, 21 were unprovoked, 5 were associated with cancer, 36 were provoked by major reversible risk factors (ie, recent surgery, plaster cast immobilization of the leg or immobilization for more than 72 hours), 20 were provoked by minor reversible risk factors (ie, air travel, pregnancy, or estrogen therapy), and risk factors were uncertain in 20.