Table 3. Nested case control study for analysis of association between being incident case and potential risk-factor.
| Risk factors | Case (n = 6) | Control (n = 44) | OR (95%CI) | P-value | |
| Gender (%) [ a ] | male | 3 | 20 | 1 | |
| female | 3 | 24 | 1.20 (0.14–9.95) | 1.0000 | |
| Cancer (%) [ a ] | yes | 6 | 37 | 1 | |
| no | 0 | 7 | na | 0.5760 | |
| HSCT (%) [ a ] | yes | 4 | 14 | 1 | |
| no | 2 | 30 | 4.29 (0.52–51.04) | 0.1710 | |
| Surgery (%) [ a ] | yes | 6 | 34 | 1 | |
| no | 0 | 10 | na | 0.3271 | |
| Transfusion (%) [ a ] | yes | 2 | 7 | 1 | |
| no | 4 | 37 | 2.64 (0.20–22.58) | 0.2629 | |
| CVC (%) [ a ] | yes | 4 | 22 | 1 | |
| no | 2 | 22 | 2.00 (0.25–23.94) | 0.6688 | |
| Median age (IQR) [ b ] | 57 (52–72) | 66 (52.5–73) | - | 0.7088 | |
| Median exposure to mp-LD (IQR) [ b - c ] | 29.5 (15–31) | 0 (0–11) | - | 0.0102 | |
| Overall | - | 6 | 44 | - | - |
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).
) 95%CI and p-value according to Fisher's exact test.
) p-value according to Mann–Whitney U test.
) 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.