Table 4.

Composite diagnostic test performance of UFC + ACTH using normal upper limit vs highest accuracy threshold

Diagnostic test, technique, and normal reference range	Highest accuracy threshold	AUCa	Sensitivity, %	Specificity, %	PPV (95% CI)	NPV (95% CI)
Composite test following highest accuracy thresholds
UFC (LC-MS/MS) + ACTH, n = 82	72.0, 39.1	0.93 (0.87,0.98)	84	100	100 (93-100)	52 (36-100)
Composite tests following standard-of-care thresholds
Pool UFC + ACTH n = 97	UFC ≥ ULN + ACTH > 20 ng/mL	0.67 (0.84,0.50)	86	47	89 (73-95)	39 (25-67)

Abbreviations: AUC, area under the curve; LC-MS/MS, liquid chromatography tandem mass spectometry; NPV, negative predictive value; PPV, positive predictive value; UFC, urinary free cortisol; ULN, upper limit of normal.

^a Comparing AUC using highest accuracy thresholds versus standard of care thresholds, P = 0.015.