Responder Profile to Pharmaceutical-Grade Chondroitin Sulfate: An Analysis of the CONCEPT Trial

INTRODUCTION: The recent CONCEPT study showed that 800 mg/day of pharmaceutical-grade chondroitin sulfate (CS) was superior to placebo and similar to celecoxib in reducing pain and improving function over 6 months in patients with symptomatic knee osteoarthritis (OA). We investigate, in the present study, whether a responder profile to CS could be defined (i.e., to determine a patient’s profile with the best response to treatment). METHODS: Subjects from the CS group of the CONCEPT study were included in the present analysis. Within the CS group, various subgroups were created on the basis of different categories of age, sex, body mass index, Kellgren and Lawrence grade, age since the beginning of OA, and baseline level of pain (i.e., VAS) or function (i.e., Lequesne index). The nonparametric Kruskal–Wallis (KW) test was applied to compare the VAS pain/Lequesne index evolutions between the subgroups, and the Dwass, Steel, Critchlow, Fligner (DSCF) procedure was used to compute multiple comparisons. The impact of various covariates on the VAS pain/Lequesne index evolution was assessed by means of multiple regression. RESULTS: Across all analyses, the probability of response to CS treatment was significantly associated with the duration between the date of diagnosis and the initiation of treatment. In other words, the shorter the interval between the diagnosis and the beginning of the treatment, the higher the response for both pain and function, particularly for patients with a duration of less than 5 years compared to patients with a duration of 10 years or more. No other criteria were found to be consistently associated with the response to CS treatment. CONCLUSION: The treatment of OA with CS has the highest chance of success if administered in the early stage of the disease. Further research with other clinical outcomes should be carried out prior to widespread application of these findings. TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT03200288.