Correcting serum concentrations of organochlorine compounds by lipids: Alternatives to the organochlorine/total lipids ratio

IntroductionWhen studying the effects of organochlorine compounds (OCs) on human health it is common to correct serum concentrations of OC by total lipids (TL). However, the relationship between serum OCs and serum TL is far from established in many diseases, including several cancers. Our aim was to analyze the relationship between serum OC and TL in patients with pancreatic ductal adenocarcinoma (PDA), and to explore several alternatives to perform the OC lipid correction.MethodsIncident cases of PDA were interviewed and had blood drawn soon around hospital admission (n = 144). Serum concentrations of OCs were analysed by high-resolution gas chromatography with electron-capture detection.ResultsMost patients with high TL had moderate or low concentrations of OCs. By contrast, the variability of OC values among patients with normal TL was large. Correlations were of a similar magnitude between OC and TL and between OC and total cholesterol; while these correlations were weak (all Spearman's ρ < 0.3 and R2 < 0.11), no OC were significantly correlated with triglycerides. Although all alternatives to the OC/TL linear ratio were statistically significant for at least one OC, their R2 was always below 10%.ConclusionsIn patients with severe diseases as PDA, linear correction of OC by TL as commonly performed in epidemiologic studies may be inappropriate. Results contribute to the scant literature on the rationale to correct serum concentrations of OC by lipids. They suggest that it is unwarranted to routinely correct OC by TL, offer ways to assess such need, and present alternatives as no TL correction, correction by total cholesterol only or use of different statistical models.