Abstract
BACKGROUND: To develop and validate patient-reported instruments, based on patients' lived experiences, for monitoring the symptoms and impact of long coronavirus disease (covid). METHODS: The 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 coronavirus disease 2019 (COVID-19) and symptoms extending over 3 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, Measure yourself medical outcome profile 2). Reliability was determined by a test-retest. The "patient acceptable symptomatic state" (PASS) was determined by the percentile method. RESULTS: Validation involved 1022 participants (55% with confirmed COVID-19, 79% female, and 12.5% hospitalized 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 .80 to .86) for the ST score and 0.84 (.80 to .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). CONCLUSIONS: The 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.