Development and validation of the long covid symptom and impact tools, a set of patient-reported instruments constructed from patients' lived experience

ObjectivesTo develop and validate patient-reported instruments, based on patients lived experiences, for monitoring the symptoms and impact of long covid. DesignThe long covid Symptom and Impact Tools (ST and IT) were constructed from the answers to a survey with open-ended questions to 492 patients with long covid. Validation of the tools involved adult patients with suspected or confirmed covid-19 and symptoms extending over three weeks after onset. Construct validity was assessed by examining the relations of the ST and IT scores with health related quality of life (EQ-5D-5L), function (PCFS, post-covid functional scale), and perceived health (MYMOP2). Reliability was determined by a test-retest. The "patient acceptable symptomatic state" (PASS) was determined by the percentile method. ResultsValidation involved 1022 participants (55% with confirmed covid-19, 79% female and 12.5% hospitalised for covid-19). The long covid ST and IT scores were strongly correlated with the EQ-5D-5L (rs = -0.45 and rs = -0.59 respectively), the PCFS (rs = -0.39 and rs = -0.55), and the MYMOP2 (rs = -0.40 and rs = -0.59). Reproducibility was excellent with an interclass correlation coefficient of 0.83 (95% confidence interval 0.80 to 0.86) for the ST score and 0.84 (0.80 to 0.87) for the IT score. In total, 793 (77.5%) patients reported an unacceptable symptomatic state, thereby setting the PASS for the long covid IT score at 30 (28 to 33). ConclusionsThe long covid ST and IT tools, constructed from patients lived experiences, provide the first validated and reliable instruments for monitoring the symptoms and impact of long covid. Short summaryWe developed the long covid Symptom and Impact Tools (ST and IT) from the experiences of 492 patients, captured during a survey with open-ended questions, and assessed their validity and reliability in a sample of 1022 patients with long covid.