Table 2

Published validation studies of bullous pemphigoid or pemphigus vulgaris diagnostic codes in EHR

PublicationDiseaseClassificationEHRPopulationValidation methodPPV (95% CI)
Hsu et al21Pemphigus* (694.4) and bullous pemphigoid (694.5)ICD-9 Clinical Modification diagnostic codesNorthwestern Medicine Electronic Data Warehouse; inpatient+outpatient dataPatients with multiple codes for either pemphigus (n=161) or bullous pemphigoid (n=126)Manual review of outpatient and inpatient records. Diagnosis was confirmed by ≥2 indicators of disease:
  • Clinical diagnosis

  • Biopsy histology

  • Direct immunofluorescence

  • Indirect immunofluorescence or ELISA

Pemphigus: 100% (96% to 100%);
bullous pemphigoid: 99% (93% to 99%)
Grönhagen et al20Bullous pemphigoid (L12.0, L12.8, L12.9)ICD-10 diagnostic codesSwedish National Patient Register;
inpatient+outpatient data
307 patients with primary or secondary diagnosis of bullous pemphigoid who had medical records available for reviewManual review of immunopathological and histopathological registries and medical records. Diagnosis was confirmed by:
  • Clear clinical history and physical examination, and

  • Positive ELISA, or

  • Histopathological or immunopathological pattern consistent with bullous pemphigoid

  • *Pemphigus vulgaris, pemphigus vegetans, pemphigus foliaceus, pemphigus erythematosus, paraneoplastic pemphigus and drug-induced pemphigus.

  • EHR, electronic healthcare record; ICD-10, International Classification of Diseases Version 10; PPV, positive predictive value.