Table 1

Distribution of benchmark blistering disease diagnoses for bullous pemphigoid and pemphigus vulgaris incident cases identified in the CPRD, shown with the PPV (95% CI) for specific, broad and combined Read codes for each disease

CPRD Read codeHospital episode diagnosis (benchmark)n% PPV (95% CI)
Bullous pemphigoidPemphigus vulgarisOther
Bullous pemphigoid
Specific (M145000)527 (95.6%)12 (2.2%)12 (2.2%)55195.6 (93.6 to 97.1)
Broad (M145.00, M145z00)216 (87.8%)12 (4.9%)18 (7.3%)24687.8 (83.1 to 91.4)
Total743 (93.2%)24 (3.0%)30 (3.8%)79793.2 (91.3 to 94.8)
Pemphigus vulgaris
Specific (M144600, M144500)2 (9.1%)18 (81.8%)2 (9.1%)2281.8 (58.8 to 93.4)
Broad (M144.00, M144z00)19 (30.2%)32 (50.8%)12 (19.1%)6350.8 (38.4 to 63.1)
Total21 (24.7%)50 (58.8%)14 (16.5%)8558.8 (48.0 to 68.9)
  • ICD-10 codes L10.0 (pemphigus vulgaris), L10.1 (pemphigus vegetans) and L10.9 (pemphigus, unspecified) are classed as a hospital episode diagnosis of ‘pemphigus vulgaris’. ICD-10 codes L12.0 (bullous pemphigoid) and L12.9 (pemphigoid, unspecified) are classed as ‘bullous pemphigoid’. All other blistering disease ICD-10 codes and where the HES algorithm generated an uncertain diagnosis (n=7 for bullous pemphigoid and n=3 for pemphigus vulgaris) are classed as ‘other’.

  • CPRD, Clinical Practice Research Datalink; HES, Hospital Episode Statistics; ICD-10, International Classification of Diseases Version 10; PPV, positive predictive value.