highly significantP < 0.001
After excluding outliers exceeding 3 standard deviations (14 T1DM samples with S1P > 2315.3 nmol/L and 9 HC samples with S1P > 761.8 nmol/L), the difference remained highly significant (606.7 ± 431.8 vs. 390.8 ± 160.5 nmol/L, P < 0.001; Table 3 ), confirming that the elevation was not driven by extreme values.