Clinical Investigation
Vitamin D Serum Level, Disease Activity and Functional Ability in Different Rheumatic Patients

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Abstract

Background

The aim of the study was to determine the serum vitamin D levels in patients with psoriatic arthritis (PsA) and compare it with patients with rheumatoid arthritis (RA) and with osteoarthritis (oA), as well as to explore the relationship of the vitamin D level with indices of disease activity and functional ability in a real-life setting in a south- European country.

Methods

In a cross-sectional study, 120 adult patients with established diagnosis of PsA, RA and oA were consecutively enrolled. Serum 25-hydroxyvitamin D and intact parathyroid hormone were determined. Parameters of disease activity and functional ability were obtained using standard instruments.

Results

Serum vitamin D insufficiency (≤ 75 nmol/L) was found in 74% of patients with PsA, 94% patients with RA and 97% of patients with OA, whereas vitamin D deficiency (≤ 25 nmol/L) was found in 13% of patients with PsA, 39% of patients with RA and in 38% of patients with OA. Compared with RA, patients with PsA had significantly higher serum vitamin D (P = 0.002), and when controlling for age and gender, their serum vitamin D level was significantly associated with disease activity and functional activity.

Conclusions

In the group of rheumatic patients, a high prevalence of serum vitamin D insufficiency/deficiency was found regardless of the type of arthritis. Patients with PsA might have higher levels of vitamin D than patients with RA, and this was associated with disease activity and functional ability. The results of this study indicate that prophylactic supplementation with vitamin D might be recommended for all rheumatic patients.

Section snippets

Subjects

Three groups of patients according to rheumatic diagnosis were consecutively enrolled from the outpatient clinics of 3 rheumatologic centers in Zagreb (Croatia) during a winter time (January-March). Two groups had inflammatory arthritis: PsA (38 patients: 19 men and 19 women), RA (53 patients: 4 men and 49 women), whereas the 3rd group consisted of patients with OA, a non-inflammatory rheumatic condition (29 patients: 5 men and 25 women).

The diagnosis of PsA, RA and OA were made according to

RESULTS

Age, clinical and laboratory parameters of patients with PsA, RA and OA are presented in Table 1. Patients with RA were significantly older than patients with PsA (P = 0.011), and patients with OA were significantly older than patients with PsA and RA (P < 0.001). Serum (25-OH)D level of < 75 nmol/L was found in 74% of patients with PsA, 94% of patients with RA and 97% of patients with OA. Vitamin D deficiency (≤ 25 nmol/L) was found in 13% of patients with PsA, 39% of patients with RA and 38% of

DISCUSSION

In this study, we wanted to analyze differences in the prevalence of vitamin D deficiency in patients with PsA, RA and OA and to explore its relationship with indices of disease activity and functional ability. In our sample of consecutive patients in outpatient rheumatology clinic, we showed that subjects with PsA, RA and OA have suboptimal levels of serum vitamin D. Vitamin D level was associated with disease activity only in the group of patients with PsA.

The association between vitamin D

CONCLUSIONS

In our patients attending general rheumatology clinic, low levels of serum vitamin D levels were found regardless of the type of rheumatic disease (inflammatory and noninflammatory). Comparing with RA, patients with PsA had significantly higher levels of serum vitamin D, and it was associated with disease activity. Their vitamin D level was also significantly associated with disease activity, which was not determined in patients with RA or OA. According to our data, routine prophylactic

ACKNOWLEDGMENTS

The authors thank Professor Maurizio Cutolo and Professor Alberto Sulli (from Research Laboratories and Clinical Academic Unit of Rheumatology, University of Genova, Italy) for reviewing the proposal of the study and for their incentive scientific advices.

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    Supported in part by the Croatian Society of Rheumatology. The article has resulted from the work on the scientific project entitled “Psoriatic arthritis—Epidemiology and risk factors of progression,” supported by the Ministry of Science, Education and Sports, Republic of Croatia (Project No. 134-0000000-3531).

    The authors have no conflicts of interest to disclose.

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