Variability in baseline laboratory measurements of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

Multi-center epidemiological studies must ascertain that their measurements are accurate and reliable. For laboratory measurements, reliability can be assessed through investigation of reproducibility of measurements in the same individual. In this paper, we present results from the quality control analysis of the baseline laboratory measurements from the ELSA-Brasil study. The study enrolled 15,105 civil servants at 6 research centers in 3 regions of Brazil between 2008–2010, with multiple biochemical analytes being measured at a central laboratory. Quality control was ascertained through standard laboratory evaluation of intra- and inter-assay variability and test-retest analysis in a subset of randomly chosen participants. An additional sample of urine or blood was collected from these participants, and these samples were handled in the same manner as the original ones, locally and at the central laboratory. Reliability was assessed with the intraclass correlation coefficient (ICC), estimated through a random effects model. Coefficients of variation (CV) and Bland-Altman plots were additionally used to assess measurement variability. Laboratory intra and inter-assay CVs varied from 0.86% to 7.77%. From test-retest analyses, the ICCs were high for the majority of the analytes. Notably lower ICCs were observed for serum sodium (ICC=0.50; 95%CI=0.31–0.65) and serum potassium (ICC=0.73; 95%CI=0.60–0.83), due to the small biological range of these analytes. The CVs ranged from 1 to 14%. The Bland-Altman plots confirmed these results. The quality control analyses showed that the collection, processing and measurement protocols utilized in the ELSA-Brasil produced reliable biochemical measurements.

Glutamic acid decarboxylase antibodies are indicators of the course, but not of the onset, of diabetes in middle-aged adults: the Atherosclerosis Risk in Communities Study

To efficiently examine the association of glutamic acid decarboxylase antibody (GADA) positivity with the onset and progression of diabetes in middle-aged adults, we performed a case-cohort study representing the ~9-year experience of 10,275 Atherosclerosis Risk in Communities Study participants, initially aged 45-64 years. Antibodies to glutamic acid decarboxylase (GAD65) were measured by radioimmunoassay in 580 incident diabetes cases and 544 non-cases. The overall weighted prevalence of GADA positivity (³1 U/mL) was 7.3 percent. Baseline risk factors, with the exception of smoking and interleukin-6 (P ú 0.02), were generally similar between GADA-positive and -negative individuals. GADA positivity did not predict incident diabetes in multiply adjusted (HR = 1.04; 95 percentCI = 0.55, 1.96) proportional hazard analyses. However, a small non-significant adjusted risk (HR = 1.29; 95 percentCI = 0.58, 2.88) was seen for those in the highest tertile (³2.38 U/mL) of positivity. GADA-positive and GADA-negative non-diabetic individuals had similar risk profiles for diabetes, with central obesity and elevated inflammation markers, aside from glucose, being the main predictors. Among diabetes cases at study's end, progression to insulin treatment increased monotonically as a function of baseline GADA level. Overall, being GADA positive increased risk of progression to insulin use almost 10 times (HR = 9.9; 95 percentCI = 3.4, 28.5). In conclusion, in initially non-diabetic middle-aged adults, GADA positivity did not increase diabetes risk, and the overall baseline profile of risk factors was similar for positive and negative individuals. Among middle-aged adults, with the possible exception of those with the highest GADA levels, autoimmune pathophysiology reflected by GADA may become clinically relevant only after diabetes onset.

Test de estimulación con progesterona en al detección de hiperestrogenismo en mujeres post-menopáusicas asintomáticas / Stimulation test with progesterone in detection of Hiperestrogenism in asintomatic post-menopausal women

Con el propósito de estudiar la utilidad del test de provocación con progesterona para la detección precoz de patología endometrial en mujeres postmenopáusicas asintomáticas; procedimos a la aplicación de 250 mg. de Caproato de Hidroxiprogesterona via intramuscular a 70 mujeres postmenopáusicas asintomáticas, captadas en el consultorio externo de Ginecología del Hospital Nacional Almanzor Aguinaga Asenjo - IPSS - Chiclayo. Se consideró el test positivo o negativo de acuerdo con la presencia o ausencia de sangrado uterino; se esperó 30 días y a todas las pacientes independientemente del resultado se sometieron a la biopsia con cureta de Novak; para posteriormente efectuarse el estudio histológico del endometrio. El test positivo mostró el 14.29 por ciento de endometrio hiperplásico en mujeres postmenopáusicas asintomáticas; permitiendo en el futuro un poder selectivo de las pacientes, puesto que el curetaje diagnóstico estará dirigido solo a las postmenopáusicas que sangran con el test y de esta manera detectar e instituir de forma precoz el tratamiento de lesiones consideradas en algunas mujeres como premalignas para el carcinoma endometrial