OBJECTIVES: Assessment of the quality of patient-reported medical information in the Dutch Biologic Monitor and evaluation of the representativeness of the sampled participants. METHODS: Consecutive adult patients using a biologic DMARD (bDMARD) for an immune-mediated inflammatory disease were included in eight Dutch centres. For this substudy, data of 550 patients with inflammatory rheumatic diseases were used. Patient-reported bDMARD prescription, indication and combination therapy were verified for patients that permitted access to their electronic health record using percentage agreement and/or Cohen's kappa (n = 483). Conservative post hoc sensitivity analysis was performed to account for missing data. Population representativeness was tested for the entire substudy population by comparing age, gender and prescribed bDMARD to the centres' reference populations using Mann-Whitney U-test, χ2 goodness-of-fit or Fisher's exact test with Monte Carlo simulation (n = 550). RESULTS: The correct bDMARD was reported by 95.8% of the participants. Agreement between patients and electronic health record was almost perfect for indications (κ = 0.832) and substantial for combination therapies (κ = 0.725). Agreement on combination therapies remained substantial after post hoc sensitivity analysis (κ = 0.640). Gender distribution (P > 0.05) and bDMARD use (P > 0.05) were similar to the reference populations. Median age was different (58.0 vs 56.0 years, P = 0.04), but considered clinically irrelevant. CONCLUSION: The Dutch Biologic Monitor seems to be a valid tool to obtain patient-reported medical information. Reported medical information generally corresponded to the electronic health records and the participants represented their reference populations regarding age, gender and prescribed bDMARD.