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

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

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)
δ	Sample size for each group	With PD	Without PD	Total
0.40	16	16	80	96	approximately 3 patients
0.30^a	24	24	120	144	approximately 4 patients
0.20	41	41	205	246	5 patients
0.10	102	102	510	612	10 patients

^δDifference in the cumulative incidence of TE in patients with and without prothrombotic defects
^aMinimal clinically important difference

ISSN: 1471-2407