Background/Purpose: Psoriatic arthritis (PsA) affects between 10-30% of patients with psoriasis (PsO), but is often missed when assessed in a dermatology clinic. The Center of Excellence for Psoriasis and Psoriatic Arthritis (CEPPA) is a specialized multidisciplinary clinic consisting of expert dermatologists and rheumatologists experienced in diagnosing PsO as well as PsA. We wanted to identify simple clinical questions and findings on physical examination for dermatologists to screen PsO patients for PsA so as to refer appropriate patients to rheumatology.

Methods: This is a cross-sectional study of all PsO patients seen by dermatologists in the CEPPA clinic since its inception in 2006 through 2010. Possibility of PsA was assessed by four screening questions: “Do you have a history of joint pain or swelling,” “Do you have morning stiffness,” “Have you ever had x-rays taken”,” and “Do you have PsA”.  Since nail involvement is known to predict development of PsA, assessment of nail changes was included as a physical finding for screening. Quality of life (QoL) measures were assessed with validated instruments (SF12, PQOL12 and RAPID3).

Results: Of 524 patients assessed in dermatology, 237 were referred to rheumatology, 34 were lost to follow up, 203 were evaluated and 128 (24.4%) were found to have PsA. Of those who answered ‘no’ to all the four screening questions 95.3 % did not have PsA. However, of those fulfilling all five parameters, including the four screening questions plus nail changes, 88.9 % had PsA.  Table shows the sensitivity, specificity, PPV and NPV for screening questions and nail changes individually and in combination. The median age (48 years) and smoking history (in 20%) was not significantly different in patients with and without PsA. The median body mass index (BMI) and PsO body surface area (BSA) were significantly higher in patients with PsA than those without [31.5(IQR 11) vs 28.6 (IQR 8) and 10% (IQR 15) vs 7% (IQR 12), respectively, p <0.01]. PsA patients were more likely to have nail changes (OR 12.4, 95% CI: 5.9 – 26.5, P < 0.01). Onset of PsO occurred 10 years earlier in patients with a family history of PsO than those without (median age 25 vs 38, p <0.01). Six percent of patients developed PsA before, 8% with and 86% after the onset of PsO. Ninety percent were diagnosed with PsA within 25 years of PsO onset. Mean delay in PsA diagnosis from onset of joint pain was 1 year. Compared to PsO patients, patients with PsA had significantly worse QoL scores (P < 0.01). Percent of BSA involvement with PsO did not correlate with any clinical variables.

Conclusion: In this large cohort of PsO patients, the prevalence of PsA was 24.4%. PsA patients had significantly worse QoL than those with PsO alone. A negative response to all four screening questions correctly ruled out the diagnosis of PsA in 95.3% of patients. Positive response to all four screening questions with PsO nail changes led to a correct diagnosis of PsA in 89% of patients.

Sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) of four screening questions and examination for psoriatic nail changes

	Sensitivity	Specificity	PPV	NPV
Do you have joint pain or swelling	88.7	54.7	41.8	93
Do you have morning stiffness	88.5	51	39.3	92.6
Do you have psoriatic arthritis	68.1	86.6	64.8	88.2
Have you ever had x-rays taken	56.6	73.2	43.2	82.4
Have you ever had x-rays taken	85.4	68.1	70.7	83.8
All five of the above	22.4	95.9	88.9	46.1

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/simple-questions-in-the-dermatology-office-may-reasonably-exclude-but-do-not-reliably-identify-psoriatic-arthritis-patients-results-from-the-center-of-excellence-for-psoriasis-and-psoriatic-arthriti/