Comparison of the single simple question and the patient acceptable symptom state in myasthenia gravis

The single simple question (SSQ) is a simple and validated question asking what percentage of normal a patient feels with respect to their myasthenia gravis (MG), with 100% being normal. Patient acceptable symptom states (PASS) are based on a dichotomous 'Yes' or 'No' response, asking whether a patient is satisfied overall with their current status and thus measures holistic satisfaction with their MG state. Both are patient-reported self-assessments but assess different dimensions of MG. The objective was to determine thresholds for the SSQ when patients with MG achieve an acceptable PASS status.

A retrospective chart review was performed of consecutive MG patients attending a neuromuscular clinic, and SSQ and PASS responses, demographic, clinical and serological characteristics and disease severity by the MG impairment index were extracted.

One hundred and fifty-seven consecutive patients were identified: 43 (27.4%) patients responded 'No' to the PASS question. Between the PASS 'Yes'/'No' groups, only SSQ (87.5 ± 13.4 vs. 52.3 ± 23.3; P < 0.001) and MG impairment index scores (9.2 ± 10.3 vs. 29.6 ± 16; P < 0.001) were significantly different. The receiver operating characteristic curve for PASS and SSQ had an area under the curve of 0.92 ± 0.024 (confidence interval 0.872-0.965, P < 0.001). An SSQ score ≥72.5% had 84.2% sensitivity and 86% specificity to classify patients as PASS positive.

The PASS and SSQ patient-reported outcomes are closely associated and a SSQ threshold ≥72.5% predicts an acceptable MG state. Other demographic and disease-related factors did not influence the PASS response in this study.