TABLE 4.

Life table estimation of cumulative incidence (risk) of recurrent parasitemia after chloroquine therapy of vivax malariaa

DayNo. of subjects remaining at riskNo. of cases of therapeutic failureNo. of subjects withdrawn for any reasonInterval riskbCumulative riskc
0340000
234210.05970.0597
4310000.0597
731310.09840.1522
1127520.19230.3152
1420400.20000.4522
1816200.12500.5207
21140100.5207
2813320.25000.6405
  • a Reprinted from reference 15 with permission of the publisher.

  • b Interval risk was calculated as follows: i = [N − (w/2)]−1, where N is the number of subjects remaining at risk, i is the number of cases of therapeutic failure, and w is the number of subjects withdrawn for any reason.

  • c The cumulative incidence of therapeutic failure (CRn) was calculated as follows: CRn = 1 − [(1 − IRn) × (1 − CFn − 1)], where IR is interval risk, n is the day of the test, and n − 1 is the prior interval. To calculate the CR for day 11, first estimate the interval risk as follows: 5[27 − (2/2)]−1 = 0.1923 and, finally, 1 − [(1 − 0.1923) × (1 − 0.1522) = 0.3152. Thus, the 11-day cumulative incidence (or risk) of therapeutic failure was 31.5%.