Comparison of a specialist haematological malignancy database against a regional cancer registry: case ascertainment and diagnostic accuracy.

No large-scale study has been performed to assess the problem of registering all subtypes of haematological malignancies. We compared registration of haematological malignancies between 1994 and 1996 by haematologists in 14 National Health Service Trusts in the Eastern part of the South Thames Region with data for the same area recorded by the Thames Cancer Registry (TCR). Case ascertainment and diagnostic accuracy were the two main outcome measures. A combined total of 4714 haematological malignancies were recorded over the 3-year period. Of these, 1329 (28%) were common to both databases, 1975 (42%) were recorded only by the TCR and 1410 (30%) were recorded only by the haematologists. Nearly one-third (31%) of all cases recorded by the TCR were death certificate-only registrations. The TCR records were obtained from 30 clinical specialities. Haematology only accounted for 35% of these cases. Discordant diagnoses were recorded in 20% of the cases that were recorded in both databases. Our data suggests that both registers have deficiencies in collecting and validating data on the incidence of haematological malignancies. To address this, a partnership was established in 1998 between haematologists in the South Thames Region and the Thames Cancer Registry. It is anticipated that engaging clinicians in the collection and validation of data will enhance the completeness of case ascertainment and improve the quality of data on haematological malignancies.