Table 4.

PPV and NPV, sensitivity, specificity for components of HF algorithm

	Number of algorithm-positive hospitalisations, sum weight* (n)†	PPV (95% CI)‡	NPV (95% CI)	Sensitivity (95% CI)	Specificity (95% CI)
All	572 (399)	89.7 (86.8 to 92.7)	93.9 (89.1 to 98.6)	45.1 (25.1 to 65.1)	99.4 (99.2 to 99.6)
ICD-9 and DRG	477 (304)	92.1 (89.1 to 95.1)	93.9 (89.1 to 98.6)	41.3 (21.6 to 61.0)	99.6 (99.4 to 99.7)
ICD-9 only	87 (87)	79.3 (70.7 to 87.9)	93.9 (89.1 to 98.6)	19.9 (4.8 to 35.0)	99.6 (99.4 to 99.8)
DRG only	8 (8)	62.5 (28.4 to 96.6)	93.9 (89.1 to 98.6)	0.79 (0.16 to 1.75)	99.9 (99.9 to 100)

*Sum weight represents the number of hospitalisations from the overall study population that would have fallen into each category when inverse probability of sampling weights were applied to the study sample.

†n represents the actual number of charts reviewed that were true positives, false positives, false negatives or true negatives in each category.

‡To create 95% CI, we used a Taylor series linearisation to calculate SEs with sampling weights.

DRG, diagnosis-related group; HF, heart failure; ICD-9, International Classification of Diseases Ninth Revision; NPV, negative predictive value; PPV, positive predictive value.