Oral Glucose Tolerance Test 90-Min Values in Prediabetes Detection: Using of Multiple Regression Analyses for Diagnostic Criteria Determination

Purpose: The aim of this study was to determine the possibility of PG90 using as an indicator of PD and reveal the optimal cut-off point for separation of normal glucose metabolism (NGM) and impaired (PD+DM) glucose metabolism (IGM) by PG90 level. Methods: 134 persons (32 men and 102 women) aged 20-79 years were examined. Glycemic levels after 30, 60, 90,120 minutes after 75 g glucose loading was performed. The HbA1C examined by the SDA1c Care (SD biosensor, Korea). Fasting and post load venous plasma glucose was determined by Precision PCx Medi Sense (Abbot, USA). Equations obtained Bby linear and multiple regression method; by applying these equations 90 minutes glycemic level post-load 75 g glucose was calculated. Qualitative characteristics of the diagnostic test were used for the evaluation of cut-off point for 90 minutes glycemic level post-load 75 g glucose. Results: The relationship between PG90 and HbA1C, PG90 and FG, PG90 and PG120 was studied by using correlation analyses. The relationship between PG90 and HbA1C (r=+0.71 [95%CI +0.615, +0.785]), PG90 and FG (r=+0.53 [95%CI +0.397, +0.641]) was as well as between PG90 and PG120 (r=+0.85 [95%CI +0.796, +0.891]). All three correlation coefficients were statistically significant, p<0.001. The equation for PG90 cut-off point was calculated by applying multiple regression analyses. It was obtained the quality characteristics of received cut-off point by equation. Maximal Index Youden had FG cut-off point “>109 mg/dl” (67.9%). Index Youden for PG90 cut-off point “>168 mg/dl” was higher than 50.0 %. Conclusion: The cut-off point PG90 may be used for NGM and PD differentiation