Ultramicro Automated Screening Method for Uric Acid

An automated colorimetric microprocedure,suitable for screening purposes,has been developed for the determination of blood uric acid levels. The method uses 2O-p.l. whole-blood (capillary) samples and is based on the AutoAnalyzer measurement of the absorbanceof the colored uric acid-phosphotungsticacid complex. The dilution inherent in the sampling procedure necessitated a modification of the existing AutoAnalyzer method to increase the sensitivity. The proposed method is evaluated for precision and accuracy by comparison with the standard AutoAnalyzer macro-method. RIG ACID LEVELS 111 human blood have been studied as being indicative of various rheumatic diseases (1) and as related to gout (2) and dia-betes (3). This study was undertaken to ascertain the feasibility of de-veloping a uric acid microassay suitable for detection of abnormalities in general population-screening programs. A microtechnic based on capillary blood samples is highly desirable for general population studies of this type because it circumvents many of the objections frequently encountered: hesitancy of the public to submit to venipuncture, problems encountered in the sampling process and storage, and stringent (and, in some cases, legal) requirements for personnel to obtain samples. The micromethod in this study is based on the Unopette (a commercially available item) system (4-7) developed by Gerarde, in which 2O-jl. samples are taken in a disposable, precali-brated capillary pipet and automatically diluted into a suitable preser-vative for storage until analysis. In the micromethod described in this study all samples are analyzed for uric acid with the AutoAnalyzer (Fig. 1). The procedure is similar to the standard macroprocedure for uric acid determinations (8), a colorimetric method based on the original Folin-Denis procedure (9)