Is there a relationship between the intermittent and constant osteoarthritis pain score (ICOAP) and pain flares in knee osteoarthritis?.

Abstract

PURPOSE: The Intermittent and Constant Osteoarthritis Pain Score (ICOAP) is a recently validated multidimensional osteoarthritis pain measure. This 11-item tool takes into account both the constant (6 items) and intermittent (5 items) pain of knee osteoarthritis (KOA) within 7 days summated to a single score. These items are scored from 0 (no pain) to 4 (extremely severe pain). The intent of this project was to assess the association and utility of ICOAP and its subscales in predicting pain flares in KOA identified by a 0-10 point numerical rating scale (NRS). METHODS: Study participants were selected from a 3-month web-based longitudinal follow up study developed to identify risk factors for KOA pain flares. Participants were requested to complete the ICOAP questionnaire at days 0, 30, 60 and 90 (control period assessment points) and at time points whenever they experienced knee pain flare (case period assessment points) during the follow up period. A KOA pain flare was defined as current pain with a greater than 2 point increase (on a 0-10point NRS) from the mildest KOA pain intensity reported at day 0. The ICOAP score at point of a KOA pain flare was used to identify whether ICOAP was associated with occurrence of a pain flare. Conditional logistic regression was used to identify the odds of association with pain flare by the individual subscales and total ICOAP. Receiver Operating Characteristic Curves (ROC curves) were used to assess the utility of the ICOAP and its subscales (immediately preceding the flare) in predicting pain flares using the pain flares identified by the numeric rating scale as the gold standard. The ICOAP value for the first flare during the follow up period was used to predict pain. RESULTS: 213 persons (61%females) with multiple KOA pain flares were selected. Their mean age was 62.1 years (SD 8.5). The mean body mass index was 29.8 kg/m2 (SD 6.5). There were 652 flares documented with 1232 control periods over a 3- month period. 325 flares had a documented ICOAP within the preceding 30 days. The time gap between control period and flare period assessment points differed between subjects with the mean time gap being 18.5 days (SD 9.3). The mean number of flares per person per month was 1.97 (SD 2.65). None of the patients had a pain flare at baseline ICOAP total, constant and intermittent subscales had a significant association with pain flare (Table 1). However, the ICOAP scores (total, constant and intermittent) did not usefully predict pain flares and demonstrated an area under the ROC curves of 0.69 (95% confidence interval (CI)0.67-0.72), 0.69 (95% CI 0.67-0.72), 0.67 (95% CI 0.64-0.69) for total ICOAP score, constant pain and intermittent pain subscales respectively. CONCLUSIONS: The total ICOAP score (as well as the Constant and Intermittent subscales) recorded at point of flare was associated with KOA pain flares identified by the NRS. However, the ICOAP and its subscales did not usefully predict a pain flare. The lack of difference between the constant and intermittent ICOAP score can be attributed to correlation of items in the two subscales. The lack of complete correlation between the ICOAP values and pain flare assessed by the NRS is possibly due to the multidimensional nature of the ICOAP in contrast to the uni-dimensional nature of NRS. (Table Presented).