Background/Purpose: Numerous studies have shown delays in diagnosis of psoriatic arthritis (PsA) among patients with psoriasis. The heterogeneous nature and frequently insidious onset of PsA may contribute to the delayed diagnosis. There are limited data about the pre-diagnosis phases of PsA. We aimed to assess health care utilization in a primary care setting during a 5-year period prior to the diagnosis of PsA in comparison to the general population.

Methods: We conducted a matched cohort study using the primary care Electronic Medical Record Administrative data Linked Database (EMRALD) in Ontario, Canada (comprised of >350 primary care physicians and >400,000 patients). EMRALD data were linked with provincial administrative data to obtain information about health care services utilization. Patients with PsA were identified using a validated algorithm (PPV 85%). The date of PsA diagnosis (index date) was defined as the first date an inflammatory arthritis billing code was administered by a rheumatologist. Five age- and sex-matched controls from the same family practice clinic were matched for each PsA case. The controls were assigned the same index date as their corresponding case. The primary outcome was visits to primary care physicians for non-specific musculoskeletal (MSK) issues during the 5-year period prior to the index date. We compared the rates of visits and the proportion of patients visiting primary care physicians between PsA and controls using GEE models with negative binomial distribution (for rates) and binary distribution (for probabilities).

Results:

We studied 462 PsA patients and 2310 matched controls with a mean (SD) age of 54.2±13.8 (55.6% females). Relative rates and odds of visits were higher in each of the 5 years prior to the index dates for PsA patients vs. controls (Figure 1 and Table 1). The odds ratios (OR) related to visiting a primary care physician for nonspecific MSK issues in patients with PsA vs. controls was 2.14 (95% CI 1.74, 2.63) in the first year prior to the index date and was similarly elevated up to 5 years prior (Table 1). Additionally, the Relative Rates (RR) for MSK-related visits prior to the index date were higher in PsA patients compared to controls (RR ranging from 1.93 to 2.12; Figure 1).

Conclusion: We identified the presence of a prolonged period of non-specific MSK symptoms occurring prior to the diagnosis of PsA, which is greater than the control group. Our findings suggest that there may be a pre-clinical phase of the disease characterized by non-specific MSK symptoms, which may lead to delays in diagnosis of PsA in the primary care setting.