Table 3.

Cut-off values of C-peptide indices for need for insulin therapy with 80% specificity. The data are re-calculated from the original data of reference [8] (unpublished data).

Parameter	Cut-off Value	Specificity (%)	Sensitivity (%)
PCPRI	1.53	80	61
FCPRI	0.87	80	45
24 h urinary C-peptide (μg/day)	36.4	80	39

PCPRI; postprandial C-peptide to glucose ratio, FCPRI; fasting C-peptide to glucose ratio. Since PCPRI was measured at 2 h after breakfast during admission, these values may not apply to outpatient settings or other ethnicities. When C-peptide is expressed in nmol/L instead of ng/mL, PCPRI of 1.53 and FCPRI of 0.87 would be 0.51 and 0.29, respectively.