DATA QUALITY IN POPULATION-BASED CANCER REGISTRATION - AN ASSESSMENT OF THE MERSEYSIDE AND CHESHIRE-CANCER-REGISTRY

Merseyside and Cheshire Cancer Registry (MCCR) data quality was assess ed by applying literature-based measures to 27942 cases diagnosed in 1 990 and 1991. Registrations after death (n = 8535) were also audited ( n = 917) to estimate death certificate only (DCO) case accuracy and th e proportion of registrations notified by death certificate (DC). Asce rtainment appeared to be high from the registration/mortality ratio fo r lung [1.01:1] and to be low from capture-recapture estimates (59.4%) , varying significantly with site from oesophagus [92.2% (95% CI 88.5- 95.9)] to breast [47.5 (95% CI 41.863.2)]. The estimated DC-dependent proportion was 20% (5601 out of 27942) with successful traceback in 35 33 out of 5601 (63.1%) cases. DCO flagging (2497 out of 27 942, 8.9%) overestimated true DCO cases (2068 out of 27942, 7.4%). The proportion of cases of unknown primary site was low (1.5%), varying significantl y with age [0-4.2%, (95% CI 2.5-5.9)] and district 10.8% (95% CI 0.3-1 .3) to 2.2% (95% CI 1.8-2.6)]. The median diagnosis to registration in terval appeared to be good (10 weeks), varying significantly with site (P < 0.0001), age (P < 0.0001) and district (P < 0.0001). The proport ion with a verified diagnosis was 77.3%, varying significantly with si te [lung 55.2% (95% CI 53.7-56.7) to cervix 96.9% (95% CI 96.3-97.5)], age [45.2% (95% CI 40.9-49.5) to 97.5% (95% CI 96.4-98.6)] and distri ct [71.8% (95% CI 69.9-73.8) to 82.5% (95% CI 80.7-84.3)]. The DCO per centages varied similarly by site [non-melanoma skin 0.4% (95% CI 0.2- 0.6) to lung 22.6% CI (95% 19.9-25.3)], age [0.7(95% CI 0.1-1.4) to 23 .0 (95% CI 19.4-26.6)] and district [6.9% (95% CI 5.7-8.1) to 13.9% (9 5% CI 12.9-15.0)]. MCCR data quality varied with age, site and distric t - inviting action - and apparently compares favourably with elsewher e, although deficiencies in published data hampered definitive assessm ent. Putting quality assurance into practice identified shortcomings i n the scope, definition and application of existing measures, and abse nt standards impeded interpretation. Cancer registry quality assurance should henceforward be within an explicit framework of agreed and sta ndardized measures.