External Validation of the Newly Developed BETA-2 Scoring System for Pancreatic Islet Graft Function Assessment.

BACKGROUND: BETA-2 score using a single fasting blood sample was developed to estimate beta-cell function after islet transplantation (ITx) and was validated internally by a high ITx volume center (Edmonton). The goal was to validate BETA-2 externally, in our center. METHODS: Areas under receiver operating characteristic curves (AUROCs) were obtained to see if beta score or BETA-2 would better detect insulin independence and glucose intolerance. RESULTS: We analyzed values from 48 mixed meal tolerance tests (MMTTs) in 4 ITx recipients with a long-term follow-up to 140 months (LT group) and from 54 MMTTs in 13 short-term group patients (ST group). AUROC for no need for insulin support was 0.776 (95% confidence interval [CI] 0.539-1, P = .02) and 0.922 (95% CI 0.848-0.996, P < .001) for beta score and 0.79 (95% CI 0.596-0.983, P = .003) and 0.941 (95% CI 0.86-1, P < .001) for BETA-2, in LT and ST groups, respectively, and did not differ significantly. In LT group BETA-2 score ≥ 13.03 predicted no need for insulin supplementation with sensitivity of 98%, specificity of 50%, positive predictive value (PPV) of 93%, and negative predictive value (NPV) of 75%. In ST group the optimal cutoff was ≥13.63 with sensitivity of 92% and specificity, PPV, and NPV 82% to 95%. For the detection of glucose intolerance BETA-2 cutoffs were <19.43 in LT group and <17.23 in ST group with sensitivity > 76% and specificity, PPV, and NPV > 80% in both groups. CONCLUSION: BETA-2 score was successfully validated externally and is a practical tool allowing for frequent and reliable assessments of islet graft function based on a single fasting blood sample.

Iodimetric determination of 2-mercaptopyrimidines.

A new method for the determination of 2-mercaptopyrimidines, using their reaction with iodine in neutral and alkaline medium, is presented. The determinability range in the volumetric titration, in phosphate buffer with starch as an indicator, was found to be equal to 40-1000 mumol for 2-mercaptopyrimidine (I) and 100-2000 mumol for 2-mercapto-4-methylpyrimidine (II), and 200-2000 mumol for 4,6-dimethyl-2-mercaptopyrimidine (III). In the volumetric titration in alkaline medium, with the potentiometric end-point detection, the determinability range is 50-250 mumol for 2-mercapto-4-methylpyrimidine (II), 50-500 mumol for 4,6-dimethyl-2-mercaptopyrimidine (III), 20-250 mumol for 4,5-diamino-2,6-dimercaptopyrimidine (IV), and 20-1000 mumol for 2-thioorotic acid (V). In the coulometric titration, using the biamperometric end-point detection, 0.1-4.0 mumol of 2-mercaptopyrimidine (I) and 0.1-5.0 mumol of 2-thioorotic acid (V) were successfully determined.