Objectives: To construct a patient self-assessment questionnaire testing whether patients can provide valid information about their skin thickness, tethering and thinness.
Methods: The questionnaire contained questions about the 17 body areas identical to those investigated in the Modified Rodnan Skin Score (MRSS). The baseline and 1 yr follow-up values of thickening, tethering and thinning were scored on a scale of 0-3, by 131 consecutive patients.
Results: The questionnaire was feasible. The test-retest reliability was good, with an intraclass correlation coefficient of 0.5-0.6. The MRSS correlated with the 17-area thickness score (rho = 0.435, P < 0.001). Both the patient-reported thickness and tethering scores and the expert-measured MRSS and tethering scores correlated highly with each other (rho = 0.523, P < 0.001 and rho = 0.637, P < 0.001, respectively). The patient-reported thinness scores did not show any correlation with the examiner-measured skin thickening/tethering. All thickness-related scores were sorted into the same factor by principal component analysis. Conversely, skin thinness scores were sorted into a distinct factor. Skin thickness scores reported by diffuse SSc patients were different from those of the limited SSc cases (P < 0.05).
Conclusions: We validated the skin thickness domain of the questionnaire, except the responsiveness. Because of the low mean MRSS of patients in this investigation, the patient self-assessment validation procedure should be repeated with cases exhibiting more extensive skin involvement. Patient-reported and examiner-measured tethering may not be used as independent instruments of skin involvement. The skin thinness domain may contain valuable independent information, therefore it also merits further investigation.