APPENDIX 2

Positive Predictive Value of International Classification of Diseases, Ninth Revision (ICD-9) Diagnosis Codes and Platelets Counts in Predicting a Confirmed Cases of Immune Thrombocytopenic Purpura upon Chart Review

Platelet CountsDiagnosis Code GroupITP CasePPV, %
YesNo
Years 2000–2004a
 1 count <50K and287.31 ITP00
 1 count <50K andOther TP codeb507041.7
 2 counts <50K andNo code21511.8
 Total528538.0
Years 2005–2008
 1 count <50K and287.31 ITP902478.9
 1 count <50K andOther TP codeb6311335.8
 2 counts <50K andNo code1204.8
 Total15415749.5
  • PPV, positive predictive value; TP, thrombocytopenic purpura; ITP, immune thrombocytopenic purpura.

  • a Immune thrombocytopenic purpura (287.31) was not routinely used until 2005.

  • b 287, 287.0, 287.1, 287.2, 287.3 287.30, 287.39, 287.4, 287.5, 287.8, 287.9.