Table 2.

Methods of validation and median percentage of cases confirmed using each method

Validation method	n validations carried out	Percentage of cases confirmed by validation Median (Range)
Internal
Manual review of computerized records or diagnostic algorithm	31	86.2 (33–100)
Sensitivity analysis	23	n/a
External
Comparison of rates	143	n/a
Additional information from GP	160	88.6 (24–100)
Questionnaire to GP only	43	91.7 (26–93)
Questionnaire and record request to GP	39	90.0 (41–100)
Record request to GP only	78	82.7 (24–100)
Total	357	88.6 (24–100)

It was a requirement for inclusion in our review for each study (with the exception of comparison of rates and sensitivity analyses) to provide a numerical estimate of the proportion of cases confirmed.