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Table 4 Sample size calculation requirements to compare cumulative TE in patients with and without prothrombotic defects

From: Evaluation for inherited and acquired prothrombotic defects predisposing to symptomatic thromboembolism in children with acute lymphoblastic leukemia: a protocol for a prospective, observational, cohort study

δ Sample size for each group Estimated sample size for proposed study (α =0.05 and β = 0.2, with 20% prevalence of prothombotic defects based on previous studies [12]) Number of patients needed to treat to prevent one event of TE (NNT)
With PD Without PD Total
0.40 16 16 80 96 approximately 3 patients
0.30a 24 24 120 144 approximately 4 patients
0.20 41 41 205 246 5 patients
0.10 102 102 510 612 10 patients
  1. δDifference in the cumulative incidence of TE in patients with and without prothrombotic defects
  2. aMinimal clinically important difference