Laboratory exams of the National Health Survey: methodology of sampling, data collection and analysis.

This article aims at describing the National Health Survey (Pesquisa Nacional de Saúde- PNS) methodology of collecting laboratory exams data.A subsample of 25% of the census tracts was selected, according to the stratification of the PNS sample, with a probability inversely proportional to the difficulty of collection. The collection of blood and urine was done in the households by a laboratory agent, among residents selected for individual interview. Due to the difficulties found in the field work, the sample did not reach the minimum expected number in some strata, and a post-stratification procedure was proposed for the data analysis.The collection of biospecimens was performed in 8,952 individuals. Laboratory tests were: glycated hemoglobin; total cholesterol; LDL cholesterol; HDL cholesterol; serology for dengue; red blood cell count (erythrogram) and white series count (leukogram); high performance liquid chromatography (HPLC) for diagnosis of hemoglobinopathies; creatinine. Theexcretion of potassium, salt and sodium and creatinine was estimated in the urine. The database of laboratory exams was weighed and made publicly available on the Oswaldo Cruz Foundation's PNS website and can be accessed without prior authorization.The total subsample of laboratory exams is of great value, since it allowed us to establish national reference parameters adequate to sociodemographic and geographic characteristics of the Brazilian population, providing relevant and complementary information for the analysis of the health situation of Brazil.