Validity of expert assigned retrospective estimates of occupational polychlorinated biphenyl exposure

Assessment of retrospective exposures based on expert judgment in case-control studies is usually of unknown validity because of the difficulty in finding gold standards for comparison. We investigated the relationship between expert-assigned retrospective occupational polychlorinated biphenyl (PCB) exposure estimates and serum PCB concentrations. Analyses were conducted on a subset of cases (n = 94) and controls (n = 96) in the multi-center National Cancer Institute, Surveillance, Epidemiology, and End Results Case-Control Study of non-Hodgkin lymphoma. Based on the subjects' lifetime work histories, an industrial hygienist assigned each job a probability of PCB exposure [<5% (unexposed), 5-<50% (possibly exposed), ≥50% (probably exposed)]. Ordinary least squares regression was used to investigate associations between the probability rating and log-transformed lipid-adjusted serum levels of 14 PCB congeners and total PCBs (ΓPCBs). Compared to unexposed participants (n = 163), those with a probably exposed job (n = 7) had serum levels that were 87% higher for ΓPCBs (95% confidence interval: 1.33-2.62) and 38% of serum level variability was explained by the probability rating. Statistically significant associations between probability ratings and serum levels for 12 of 14 individual congeners were also observed. In summary, the observed contrast in PCB serum levels by probability rating provides support for the occupational PCB exposure assessment.