Table 2

The positive predictive value (PPV) and proportion of patients diagnosed with chronic obstructive pulmonary disease within each algorithm

AlgorithmEligible populationQuestionnaires sent outValid returned questionnaires (n, %)Confirmed asthma casesPPV (95% CI)
Specific asthma code + reversibility testing + medication36 5169268 (60)6186.8 (78.5 to 95.0)
Specific asthma code + reversibility testing38 7969057 (63.3)5186.0 (76.7 to 95.3)
Specific asthma code + medication169 5748960 (67.4)5183.3 (73.6 to 93.0)
Specific asthma code188 1338459 (70.2)5186.4 (77.4 to 95.4)
Non-specific asthma code + reversibility testing + medication33 2807854 (69.2)4990.7 (82.8 to 98.7)
Symptoms + reversibility testing + medication53 1178755 (63.2)3256.4 (42.8 to 69.9)
Symptoms + reversibility testing66 4778858 (65.9)2643.1 (30.0 to 56.2)
Symptoms + medication190 7537864 (82.1)3857.8 (45.4 to 70.2)
  • Medication use was defined as two prescriptions within 365 days. Evidence of reversibility testing does not hold information on the outcome of these tests.