Comparison of Spectrophotometric and Fluorimetric Methods in Evaluation of Biotinidase Deficiency

BACKGROUND Biotin, a water-soluble vitamin, is used as a co-factor by enzymes involved in carboxylation reactions. Biotinidase (BTD) catalyzes the recycling of biotin from endogenous and dietary sources. Biotinidase deficiency (BD) is an autosomal recessively inherited disorder of biotin recycling that is associated with neurologic and cutaneous consequences when untreated. The aim of the study was to compare the results of spectrophotometric and fluorimetric methods, as well as to evaluate the advantages and disadvantages of both methods in current research practices. METHODS Study group was chosen among the BD suspected newborn, children and parents (n = 52) who applied to Hacettepe University Pediatric Metabolism Unit. RESULTS BTD activity is stable for 2 hours at room temperature and at 4 °C, and for 4 months at -20 °C and -80 °C. Genetic and clinical results showed that 25% of the total number of patients had complete BD which was treated with 10 mg/day biotin, while 15.38% of the patients had partial BD, and they were prescribed biotin 5 mg/day. The area under the ROC curve was 0.960±0.25 and 0.927± 0.41 for the fluorimetric and spectrophotometric method, respectively. Fluorimetric method showed 100% sensitivity and 97% specificity, whereas spectrophotometric method showed 90.5% sensitivity and 93.7% specificity. CONCLUSIONS Fluorimetric method is superior to the spectrophotometric method due to higher sensitivity and specificity.