Identifying Non-Steroidal Anti-Inflammatory Drug (NSAID) Users Among People with Osteoarthritis Through Administrative and Clinician-Reported Data – A Validation Study of 116,162 Patients

Abstract

Purpose

(i) To report the prevalence of participants to a first-line intervention for OA in Sweden using over-the-counter (OTC) and/or prescribed NSAIDs; (ii) To estimate the accuracy of dispensed prescriptions of NSAIDs recorded in a Swedish health-care register to capture the use of NSAID considering clinician-report as reference standard.

Methods

Register-based study. We used data from OA individuals who participated in the Swedish first-line intervention recorded in the Swedish Osteoarthritis Register (SOAR). SOAR includes clinician-reported use of NSAIDs in the three months preceding the intervention. We used the Prescribed Drug Register to retrieve data on NSAID prescriptions dispensed in the same period. We estimated the prevalence of OTC users (individuals with clinicians-reported use of NSAID but no prescription dispensed), prescription users (individuals with clinicians-reported use of NSAID and a prescription dispensed) and non-users (neither of the previous). We calculated sensitivity, specificity, positive predictive value, and negative predictive value of dispensed prescriptions of NSAIDs vs clinician-report.

Results

We included 116,162 individuals (mean age [Standard Deviation]: 66 [9.6] years, 79% women, 77% knee OA). Overall, 24.7% (95% Confidence Intervals [CI] 24.5%; 25.0%) used OTC NSAIDs only, 18.2% (18.0%; 18.5%) used prescribed NSAIDs, 6.6% (6–4%; 6.7%) reported not using NSAIDs while having an NSAID prescription dispensed. Of the 49,913 individuals with clinician-reported use of NSAIDs, 21,190 had a prescription dispensed (sensitivity: 42.5% [95% CI 42.0%, 42.9%]; positive predictive value: 73.5% [73.0%, 74.0%]). Of the 66,249 individuals reporting not using NSAIDs, 58,617 did not have a prescription dispensed (specificity: 88.5% [88.2%, 88.7%]; negative predictive value: 67.1% [66.8%, 67.4%]).

Conclusion

Overall, 24.7% of participants in a first-line intervention for OA used OTC NSAIDs only while 18.2% used prescribed NSAIDs. Dispensed prescriptions of NSAIDs have high specificity but low sensitivity and can correctly identify about 70% of both the non-users and users in this population.

Keywords:

• osteoarthritis
• NSAID
• register
• validation

Data Sharing Statement

The data used in this study can be obtained directly from the relevant agencies (https://www.vgregion.se; https://www.socialstyrelsen.se).

Acknowledgment

This study was also presented at the Osteoarthritis Research Society International (OARSI) conference as an abstract presentation with interim findings. The poster’s abstract was published in Osteoarthritis and Cartilage, Volume 31, S235 - S236; DOI: https://doi.org/10.1016/j.joca.2023.01.232. We would also like to acknowledge the SOAR, and the National Board of Health and Welfare, Sweden, for accessing their databases. The interpretation and conclusions contained in this study are those of the authors alone. We would also like to thank all the participants to the intervention recorded in SOAR for agreeing for their data to be used for research purposes.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

This study had no financial competing interests. Dr Ali Kiadaliri reports personal fees from Joint Academy, outside the submitted work. Professor Martin Englund reports grants from Swedish Research Council, Governmental Funding of Clinical Research within National Health Service (ALF), The Swedish Rheumatism Association, Österlund Foundation, and Gustav V’s 80-year Birthday Foundation, during the conduct of the study. The authors declare that they have no other conflicts of interest.

Additional information

Funding

The study was funded by the Swedish Research Council, Greta and Johan Kock Foundations, The Swedish Rheumatism Association, Österlund Foundation, Governmental Funding of Clinical Research within National Health Service (ALF) and the Faculty of Medicine, Lund University, Sweden.