RECALL BIAS IN A CASE-CONTROL STUDY OF LOW-BIRTH-WEIGHT

The role of report/recall bias in case-control studies of low birth we ight (LEW) was investigated in women who gave birth at a tertiary hosp ital. Prenatal exposure information reported at the postpartum intervi ew was compared with that documented during pregnancy in obstetric rec ords. 169 cases of LEW and 198 controls were selected. The two sets of information on case mothers and control mothers were compared, using the medical record as a reference. Kappa values were estimated. No tre nd was observed to increase/decrease the sensitivity and specificity o f recall. Agreement on alcohol use was very low (kappa = 0.11 for case mothers and 0.03 for control mothers): on obstetrical records, only 1 2 mothers of cases reported habitual alcohol intake at the first prena tal care visit, whereas in the interview 69 said yes to the same quest ion; in control mothers, the figures were 4 and 89 respectively. Odds ratios (ORs) of exposure estimated from the two sets of data did not d iffer importantly in 8 variables. Interview data yielded ORs for hyper tension (8.39 versus 4.63), anemia (0.44 versus 0.99) that were farthe r from the null, and ORs in the opposite direction for alcohol (0.83 v ersus 1.61) and any drug (0.64 versus 1.42). In conclusion, given that OR figures are similar for most variables and no trend is observed in sensitivity/specificity, mothers of normal births can be an adequate reference group, using personal interviews to obtain information on li festyle, and medical records for conditions.