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Table 2 Performance characteristics of ICD-9-based algorithms for the diagnosis of avascular necrosis (AVN)

From: Administrative Algorithms to identify Avascular necrosis of bone among patients undergoing upper or lower extremity magnetic resonance imaging: a validation study

Algorithms Sensitivity %, (95% CI) Specificity %, (95% CI) PPV %, (95% CI) LR+ (95% CI)
A: ≥1 ICD-9 code for AVN 81.9 (72.0–89.5) 99.6 (99.4–99.7) 66.0 (56.0–75.1) 190.0 (134.5–268.5)
B: ≥2 ICD-9 codes for AVN at least 7 days apart 57.8 (46.5–68.6) 99.9 (99.8–99.9) 81.4 (69.1–90.3) 426.7 (229.9–792.1)
C: ≥2 ICD-9 codes for AVN at least 30 days apart 44.6 (33.7–55.9) 99.9 (99.8–99.9) 78.7 (64.3–89.3) 361.8 (186.2–703.1)
D: ≥3 ICD-9 codes for AVN at least 30 days apart 44.6 (33.7–55.9) 99.9 (99.8–100.0) 82.2 (67.9–92.0) 452.3 (217.3–941.4)
  1. All ICD-9 codes occurred within 6 months of MRI.
  2. Abbreviations: ICD-9 International Classification of Diseases, 9th version, CI Confidence Interval; PPV Positive Predictive Value, LR + Positive Likelihood Ratio
  3. The sensitivity of algorithm C is actually 44.578 and specificity of 99.877, whereas the sensitivity of algorithm D is 44.578 and the specificity is 99.901, accounting for the discrepancy in the observed likelihood ratios of algorithm C and D.