Application of Competitive Binding Assay Methods to Serum Vitamin D Levels in Health And Disease

Abstract

Competitive Binding Assay methods have been used to determine the serum levels of 25- hydroxyvitamin D^ in healthy Ghanaians and patients suffering from cirrhosis of the liver and chronic renal failure. Although the assay followed fairly standard methods as used by several workers, an improvement in stability and sensitivity was obtained by the use of gelatin in the buffer; the final assay buffer being 0.02M phosphate buffer, pH 7 ,C with 0.1% gelatin. Though rachitic rat serum was used for the main part of the work, it was confirmed that normal rat serum contained the binding protein at a suitable titre for the assay as has been reported in the literature. The normal circulating levels in 47 healthy Ghanaians was 129.0 + 55.7 ng/ml sermn, 46.0 + 16.1 ng/ml*?-.t^) for 11 patients with cirrhosis of the liver and 83.5 + 82.7 ng/ml for 8 patients suffering from chronic renal failure. Both patients'lavels were significantly different from the normal mean value ( P < 0 . 0 5 ) .