Table 2: Calculation of odds ratio of potential risk factors.

Cases
(%)
Controls
(%)
Odds ratio (CI)NBTC-Lomé* (%)

Blood group A19 (23,2)39 (23,8)OR = 0,97 (IC = 0,49–1,89)21,1
Blood group B22 (26,8)49 (29,9)OR = 0,86 (IC = 0,46–1,62)25,6
Blood group AB2 (2,4)9 (5,5)Fisher exact test: 4,7
Blood group O39 (47,6)67 (40,9)OR = 1,31 (IC = 0,74–2,32)48,6
Rhesus positive74 (90,2)153 (93,3)OR = 0,67 (IC = 0,24–1,9)91

*NBTC: National Blood Transfusion Centre (mean of years 2006, 2007, 2008).
Fisher exact test used for frequencies less than 5.
OR: odds ratio.