Table 3.

PPV and NPV, sensitivity, specificity for overall HF hospitalisation identification algorithm,* weighted analysis

	Confirmed HF hospitalisation, sum weight† (n)‡	Confirmed non-HF hospitalisation, sum weight (n)	Total hospitalisations, sum weight (n)	Performance metric (95% CI)§
HF algorithm positive	513 (354)	59 (45)	572 (399)	PPV 89.7 (86.8 to 92.7)
HF algorithm negative	624 (6)	9570 (92)	10 194 (98)	NPV 93.9 (89.1 to 98.6)
Total	1138 (360)	9628 (137)	10 766 (497)
Validity measure	Sensitivity (95% CI) 45.1 (25.1 to 65.1)	Specificity (95% CI) 99.4 (99.2 to 99.6)

*The HF algorithm consisted of a primary discharge diagnosis ICD-9 code 425.X, 428.X, 402.01, 402.11, 402.91, 404.01, 404.03, 404.11, 404.13, 404.91, 404.93 or 398.91 and/or a DRG code 127 or 291–293.

†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% CIs, 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.