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

Objectives

To develop and validate patient-reported instruments, based on patients' lived experiences, for monitoring the symptoms and impact of long covid.

Design

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 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.

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 (r_s = -0.45 and r_s = -0.59 respectively), the PCFS (r_s = -0.39 and r_s = -0.55), and the MYMOP2 (r_s = -0.40 and r_s = -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).

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.