Noninvasive skin fluorescence spectroscopy for detection of abnormal glucose tolerance

The ENGINE study evaluated noninvasive skin fluorescence spectroscopy (SFS) for detection of abnormal glucose tolerance (AGT). The AGT detection performance of SFS was compared to fasting plasma glucose (FPG) and hemoglobin A_1C (A1C). The study was a head-to-head comparison of SFS to FPG and A1C in an at-risk population of 507 subjects, with no prior diagnosis of diabetes, each of whom received a 75 g, two-hour oral glucose tolerance test (OGTT). Subjects were measured by SFS on multiple days in fasting and non-fasting states. SFS data were acquired and analyzed with the SCOUT DS^® device (VeraLight, Albuquerque, NM, USA). Disease truth was AGT, defined as OGTT ≥ 7.8 mmol/L. Sensitivity, false positive rate (FPR), ROC area, and equal error rate (EER) for detection of AGT were computed. The reproducibility of SFS and FPG was assessed. The AGT sensitivity of SFS at the device's recommended screening threshold of 50 was 75.2%, higher than that of FPG (thresholds of 5.6 mmol/L or 6.1 mmol/L) and A1C (thresholds of 5.7% or 6.0%). The SFS FPR was 42.1%, comparable to an A1C threshold of 5.7% (FPR = 43.5%). The EERs of SFS, FPG and A1C were similar, as were the partial ROC areas for FPRs of 20-50%. The reproducibility of SFS was 7.7% versus 8.1% for FPG. SFS had similar AGT detection performance to FPG and A1C and is a viable alternative to screening individuals for AGT.