Nested case control study for analysis of association between being incident case and potential risk-factor.

All the 50 susceptible patients enrolled in the historical cohort (i.e. patients admitted to oncohematology unit between 4 May 2006 and 21 February 2007) were included in the risk analysis. Case were all patients defined as “incident cases” while control were all patients still “susceptible” ≥6 months after their last admission to the oncohematology unit. The results of the risk analysis provided good evidence of association between the time of exposure to multi-patient lancing devicewhile admitted with the index case and the HBV infections.OR = odds ration; 95%CI = 95% confidence interval; mp-LD = multi-patients lancing device, HSCT = hematopoietic stem cells transplant; CVC = central venous catheter; na = not any, Fisher confidence levels not possible with zero count cells (all cases were exposed).a) 95%CI and p-value according to Fisher's exact test.b) p-value according to Mann–Whitney U test.c) This represents patients' median exposure (in days) to multi-patient lancing device while admitted with the index case and until the onset of acute hepatitis or the first positive test for HBV.