Validation of ICD-9-CM/ICD-10 coding algorithms for the identification of patients with acetaminophen overdose and hepatotoxicity using administrative data

Table 4 Operating characteristics of the acetaminophen overdose algorithm according to the development of hepatotoxicity

	Sensitivity (95% CI)	Specificity (95% CI)	PPV (95% CI)	NPV (95% CI)	C-statistic (95% CI)
No hepatotoxicity (n = 112)
Overall	94% (86–98%) (66/70)	83% (69–93%) (35/42)	90% (81–96%) (66/73)	90% (76–97%) (35/39)	0.89 (0.82–0.95)
ICD-9-CM	94% (82–99%) (44/47)	81% (61–93%) (21/26)	90% (78–97%) (44/49)	88% (68–97%) (21/24)	0.87 (0.79–0.96)
ICD-10	96% (78–100%) (22/23)	88% (62–98%) (14/16)	92% (73–99%) (22/24)	93% (68–100%) (14/15)	0.92 (0.82–1.00)
Hepatotoxicity (n = 69) *
Overall	86% (75–93%) (59/69)	N/A	100% (NA) (59/59)	0% (NA) (0/10)	N/A
ICD-9-CM	88% (74–96%) (37/42)	N/A	100% (NA) (37/37)	0% (NA) (0/5)	N/A
ICD-10	81% (62–94%) (22/27)	N/A	100% (NA) (22/22)	0% (NA) (0/5)	N/A

* Hepatotoxicity as defined by the following diagnostic codes: hepatic necrosis (570, K71.1), toxic hepatitis (573.3, K71.2, K71.6, K71.9), and hepatic encephalopathy (572.2, K72.0, K72.9). Because hepatotoxicity cases had acetaminophen overdose by definition, the PPV of the overdose algorithm is 100% in these cases. For the same reason, the specificities and c-statistics cannot be calculated, and the NPVs are 0%.
CI, confidence interval; NPV, negative predictive value; NA, not applicable; PPV, positive predictive value.

ISSN: 1472-6963