Validity of self-reported mammography uptake in the Belgian health interview survey: selection and reporting bias

The validity of self-reported mammography uptake is often questioned. We assessed the related
selection and reporting biases among women aged 50–69 years in the Belgian Health Interview Survey (BHIS)
using reimbursement data for mammography stemming from the Belgian Compulsory Health Insurance organizations
(BCHI). Methods: Individual BHIS 2013 data (n¼1040) were linked to BCHI data 2010–13 (BHIS–BCHI
sample). Being reimbursed for mammography within the last 2-years was used as the gold standard. Selection
bias was assessed by comparing BHIS estimates reimbursement rates in BHIS–BCHI with similar estimates from the
Echantillon Permanent/Permanente Steekproef (EPS), a random sample of BCHI data, while reporting bias was
investigated by comparing self-reported versus reimbursement information in the BHIS–BCHI. Reporting bias was
further explored through measures of agreement and logistic regression. Results: Mammography uptake rates
based on self-reported information and reimbursement from the BHIS–BCHI were 75.5% and 69.8%, respectively.
In the EPS, it was 64.1%. The validity is significantly affected by both selection bias frelative size¼8.93% [95%
confidence interval (CI): 3.21–14.64]g and reporting bias [relative size¼8.22% (95% CI: 0.76–15.68)]. Sensitivity
was excellent (93.7%), while the specificity was fair (66.4%). The agreement was moderate (kappa¼0.63).
Women born in non-EU countries (OR¼2.81, 95% CI: 1.54–5.13), with high household income (OR¼1.27, 95%
CI: 1.02–1.60) and those reporting poor perceived health (OR¼1.41, 95% CI: 1.14–1.73) were more likely to
inaccurately report their mammography uptake. Conclusions: The validity of self-reported mammography uptake
in women aged 50–69 years is affected by both selection and reporting bias. Both administrative and survey data
are complementary when assessing mammography uptake.