Head-Eye movement control tests in patients with chronic neck pain; Inter-observer reliability and discriminative validity
BACKGROUND
Head-eye movement control deficit is an identified problem in patients with chronic neck pain, particularly in cases of whiplash associated disorders (WAD). To date, there is no evidence concerning the reliability and validity of visually assessed active head-eye movement control tests. Therefore, the objectives of the present cross-sectional study were, a) to develop a test battery; and b) to investigate inter-observer reliability and discriminative validity in patients with chronic neck pain compared to healthy controls.


METHODS
The study was conducted at two physiotherapy clinics in Switzerland. Ethics Committee approval was obtained. Ten active head-eye coordination tests, on 23 patients with chronic neck pain and associated symptoms and 19 healthy controls, were videotaped. The tests included eye movements in the neutral head position and 45° relative neck rotation, gaze stability and sequential head-eye movements. All tests were performed in the sitting and standing positions. Two blinded physiotherapists independently rated the randomized videos. Performance was rated as "negative", "moderately positive" or "clearly positive". Weighted kappa (wK) and 95% confidence intervals (CI) were calculated to investigate inter-observer reliability. Good reliability was defined as wK >0.5 with a lower boundary of 95% CI >0.2. Odds ratios (to define cut-off points) and the distribution of the classificator, numbers of positive tests, were calculated.


RESULTS
Three out of ten tests showed "excellent" (wK 0.82 to 0.86), five out of ten tests showed "substantial" (wK 0.69 to 0.79) and two out of ten tests showed "moderate" (wK 0.54 to 0.59) reliability. Results were comparable in the sitting and standing positions. On average, three out of five tests were rated positive in patients and one out of five tests was rated positive in healthy controls. An odds ratio of 13.3 to 18.6 was obtained using ≥2/5 tests as a cut-off point.


CONCLUSION
Visual assessment by physiotherapists of head-eye movement control tests is reliable. The test battery is able to discriminate between patients with chronic neck pain and healthy controls. There were no differences in performance between the sitting and standing positions. The test battery can therefore be reduced to five tests. Further research is needed to identify the test-retest stability and responsiveness.