Whether organochlorine blood levels in fasting and postprandial specimens provide equivalent measures of exposure and the extent to which collecting blood in tubes containing material to separate serum and blood cells corrupts the specimen are unclear. In this paper, we present data from two studies that address both of these issues. In the first study, 27 women provided fasting blood in plain, silicone-coated Vacutainer tubes (red-topped) and in similar tubes containing serum separator gel (SSTs), as well as a postprandial specimen in a red-topped tube. The specimens collected in SSTs were left to stand overnight, with the gel in contact with the sample. In the second study, the blood of 12 industrial incinerator workers was collected in red-topped tubes and in SSTs. Blood in SSTs was left in contact with the gel for 5 days. Serum organochlorine residue levels ([1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene] (DDE)) and polychlorinated biphenyls) in samples collected in red-topped tubes were highly correlated with levels measured in samples collected in SSTs (all Pearson r values were > or = 0.79). Postprandial and fasting organochlorine levels were also highly correlated (Pearson r values > or = 0.89). Our results indicate that timing of the collection of blood in relation to meals and use of SSTs to collect blood specimens did not greatly affect the relative classification of subjects with respect to serum level of DDE or polychlorinated biphenyls. The longer the specimen was in contact with the SST gel, however, the lower the level of organochlorine that was detected and, at least for DDE, the greater the misclassification caused.

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