Differentiating Inflammatory Arthritis from Non-Inflammatory Arthritis in Patients with Knee Mono Arthritis Using IL-17

Objective: Arthritis is one of the most common diseases in patients who have joint problems. Based on a patient’s WBC and polymorphonuclears count, it is divided into inflammatory and non-inflammatory types. IL-17 is an important cytokine causing inflammation in synovia. The objective of this research is to measure the level of IL-17 in joint fluid in order to differentiate inflammatory from non-inflammatory arthritis. Methods: In this case-control study, 40 cases were chosen: 20 patients who have inflammatory knee mono arthritis and 20 with non-inflammatory knee mono arthritis. Their demographic information including age, sex, and duration of disease was recorded by the questioners. After the patients’ consent was obtained, we sent their joint fluid samples to the lab to measure their levels of IL-17. Arthritis was considered inflammatory if there was more than 2000 WBC in one milliliter of joint fluid and non-inflammatory if there was less than 2000. We measured IL-17 using ELISA with KOMA BIOTECH kits. We analyzed the data using SPSS software. Results: In this study we had 18 males (45% of cases) and 22 females (55% of cases).The mean age and the duration of disease were 48+_15.96 Y and 8+_4.8 W respectively. Women had 40.9% inflammatory arthritis and 59.1% non-inflammatory arthritis. Men had 61.1% inflammatory and 38.9% non-inflammatory arthritis. No significant statistical difference was observed between the two groups (P-value=0.2). The means of age in patients who had inflammatory and non-inflammatory arthritis were 38.45+_13.44 and 57.55+_12.24 respectively which had a significant statistical difference (P-value<0.001). The means of disease duration in inflammatory and non-inflammatory arthritis were 5.84+_8.95 and 7.1+_3.24 W respectively (P-value=0.23). The means of the level of IL-17 in cases of inflammatory and non-inflammatory arthritis were 16.04+_5.74 and 8.83+_1.86pg/ml respectively which also had a significant statistical difference (P-value<0.001). To find a cut-off-point for IL-17 to differentiate the diagnosis of inflammatory from non-inflammatory arthritis we used an ROC diagram. The level of 10.5pg/ml of IL-17 is the cut-off-point to differentiate inflammatory from non-inflammatory knee mono arthritis. At this cut-off-point specificity, sensitivity, positive predictive value, and negative predictive value were 0.95, 0.90, 0.90, and 0.95 respectively. Conclusion: This study showed that by measuring the level of IL-17 in a patient, we can differentiate inflammatory from non-inflammatory arthritis.