Table 2.

Diagnostic performance of lupus nephritis (LN) International Classification of Diseases (ICD) codes

Test set	Diagnostic criteria	LN definition	Sensitivity, %	Specificity, %	PPV, %	NPV, %	Accuracy, %
UCSF	≥1 ICD code	Strict	56	94	83	81	81
		Inclusive	51	97	91	74	78
	≥2 ICD codes, ≥30 days apart	Strict	50	96	85	79	80
		Inclusive	43	95	85	71	74
ZSFG (external set)	≥1 ICD code	Strict	73	92	85	83	84
		Inclusive	65	93	88	76	80
	≥2 ICD codes, ≥30 days apart	Strict	55	95	88	76	79
		Inclusive	50	96	92	69	75

Performance of LN diagnosis codes for identifying prevalent cases of LN.

Inclusive, definite LN, potential LN or diagnostic uncertainty; NPV, negative predictive value; PPV, positive predictive value; Strict, definite LN only; UCSF, University of California San Francisco; ZSFG, Zuckerberg San Francisco General.