Direct LC-MS/MS and indirect GC–MS/MS methods for measuring urinary bisphenol A concentrations are comparable
- DOI
- Language of the publication
- English
- Date
- 2021-09-16
- Type
- Article
- Author(s)
- Ashley-Martin, Jillian
- Gaudreau, Éric
- Dumas, Pierre
- Liang, Chun Lei
- Logvin, Agata
- Bélanger, Patrick
- Provencher, Gilles
- Gagne, Sebastien
- Foster, Warren
- Lanphear, Bruce P.
- Arbuckle, Tye E.
- Publisher
- ScienceDirect
Abstract
Background Bisphenol A (BPA) is typically measured in urine using an indirect method that involves enzymatic deconjugation and extraction. In contrast, the direct method measures free and conjugated BPA concurrently and sums them to estimate urinary BPA concentrations. Statistical comparison of total BPA results using the direct and indirect methods is necessary to accurately interpret biomonitoring data for risk assessments. Objectives To compare urinary BPA concentrations estimated from the indirect and direct methods in duplicate first trimester urine samples collected from 1879 pregnant women from the MIREC Study. Methods For the indirect method, we measured urinary BPA concentrations using GC–MS/MS. For the direct method, we summed free and conjugated BPA concentrations measured using LC-MS/MS. We evaluated deviation between the two methods using the Bland-Altman analysis in the total sample and stratified (1) by specific gravity and (2) at the limit of quantification (LOQ). Results Median urinary BPA concentrations for the direct and indirect methods were 0.89 µg BPA equivalents/L and 0.81 µg/L respectively. Concentrations from the direct method were, on average, 8.6% (95% CI: 6.7%, 10.5%) higher than the indirect method in a Bland-Altman analysis. The percent differences between the two methods was 4.0% in urines with specific gravities < 1.02 (n = 1348, 72%) and 20.3% in urine with specific gravity ≥ 1.02. In values below the LOQ (n = 663, 35%), we observed smaller average percent deviation (4.8%) between the two methods but wider limits of agreement. Discussion Results from this study, based on the largest statistically rigorous comparison of the direct and indirect methods of BPA measurement, contrast previous findings reporting that the indirect method underestimates total BPA exposure. The difference in urinary BPA concentrations we observed with the indirect and direct methods is unlikely to alter the interpretation of health outcome data.
Plain language summary
Health Canada helps to protect the health of Canadians by assessing and managing the health risks associated with exposure to environmental contaminants. This research addresses a controversy in the literature regarding measurement of urinary bisphenol A (BPA) using the traditional indirect method vs the more recently developed direct method. Statistical comparison of total BPA results using the direct and indirect methods is necessary to accurately interpret biomonitoring data for risk assessments of BPA. This study compared urinary BPA concentrations estimated from the indirect and direct methods in duplicate first trimester urine samples collected from1,897 pregnant women enrolled in the Maternal-Infant Research on Environmental Chemicals (MIREC) study. The Institut national de santé publique du Québec (INSPQ) measured urinary BPA concentrations using both methods. Researchers used statistical models to compare total BPA concentrations between the two methods in the whole sample of pregnant women as well as in subgroups with higher urinary specific gravity (density). Median urinary BPA concentrations for the direct and indirect methods were 0.89 BPA µg equivalents/L and 0.81 µg/L respectively. Concentrations from the direct method were, on average, 8.6% higher than the indirect method. The differences between the two methods was highest in samples with more dense urines. This study demonstrates, using the most rigorous statistical methods and largest population to date, that differences between the two methods for assessing urinary BPA concentrations are unlikely to alter the interpretation of exposure and health outcome data. This study can help reduce uncertainties associated with the measurement of environmental chemicals and subsequently increase confidence in the use of these methods by Health Canada and other national and international programs.
Subject
- Health,
- Health and safety