Validity of a population-based cancer register in Sweden--an assessment of data reproducibility in the South-East Region Prostate Cancer Register.
BACKGROUND
With a population-based setting, high coverage and accurately recorded data, the validity of a register is guaranteed. The South-East Region Prostate Cancer relies on the National Cancer Register as a basic source of data, thereby ensuring a high coverage of the corresponding geographic area. To assess the reproducibility of the data recorded a random sample of the cases were reviewed a second time and compared to the original recording.


METHODS
The South-East Region Prostate Cancer Register was started in 1987. In addition to the basic data acquired from the Swedish National Register, it also includes tumour stage, grade, treatment and, since 1992, PSA. In the first stage of quality assessment 10 cases for each of the years 1987-1996 from Linköping University Hospital were randomly selected for two independent recodings according to the same protocol as the original registration. In the second step 10 cases each for the same years from the remaining 8 hospitals in the region were selected for a single recoding.


RESULTS
No systematic deviations were seen between the two independent recodings from Linköping, a single recoding was therefore considered sufficient for assessing the reproducibility of the data from the remaining hospitals in the region. The Kappa values for agreement between the original registration and the single recoding ranged from 0.589 to 0.869.


CONCLUSIONS
The population-based setting and high coverage guarantees the external validity of the register. The internal validity is ensured by the high reproducibility shown in the present study.
Centre of Oncology, University Hospital, SE-581 85 Linköping, Sweden. gabsa@ibk.liu.se
Gabriel
G
Sandblom
Monika
M
Dufmats
Mats
M
Olsson
Eberhard
E
Varenhorst
D006801:Humans; D008297:Male; D017430:Prostate-Specific Antigen; D011471:Prostatic Neoplasms / Q000453:epidemiology* / Q000473:pathology; D011786:Quality Control; D012042:Registries; D015203:Reproducibility of Results; D013548:Sweden / Q000453:epidemiology
D017430:Prostate-Specific Antigen