This multicenter study was performed to estimate the health utility value and its clinical and socio-demographic determinants among newly treated patients from COVID-19 disease. The overall mean (median) of the disease is obtained as 0.863 (0.909). This means that patients who suffer from COVID-19 lost an average of 13.7% of their HRQoL. However, if we exclude non-traders from the analysis, the mean (median) of the disease will increase significantly to 0.793 (0.848). In other words, people who are severely affected by the disease lose an average of 20.7% of their HRQoL. The findings indicate that 33.35% of the respondents did not accept any time trade-off to get perfect health, meaning that they considered the disease's effects very insignificant and thought that there was no threat to their health. Further analysis of the data confirms this claim, as 57.29% of non-traders were quarantined at home, compared to 35.60% for traders. Besides, the overall mean of hospitalized days for non-traders and traders was 3.16 and 3.88 days, respectively.
As expected, there was a significant negative association between the severity of COVID-19 disease and the disease utility. As the highest mean utility values were observed for those patients that quarantined at home (0.896) and had minor lung infection (0.927), and the lowest mean utility values belong to the participants who intubated (0.629) and had severe lung involvement (0.651). In other words, patients who have intubated or had severe lung involvement lost 37.1% and 34.9% of their HRQoL, respectively. However, we do not observe such statistically significant associations for SpO2 levels and the number of hospital days. These results suggest that variables of the patient's hospitalization and lung health status are appropriate indicators for defining the quality of life and measuring the effects of COVID-19 disease on patients' health. However, the two-limit Tobit regression analysis results confirm only the patient's hospitalization status as representing the factor of the patient's HRQoL. Depending on the patient's hospitalization status, a statistically significant difference is seen in the average hospitalization days. This amount was 12.75, 9.31, and 3.19 days for patients admitted to the ICU with intubation and without intubation, as well as hospitalization in the general ward, respectively.
The findings showed that the severe symptoms of COVID-19 disease were significantly higher among the elderly than other age groups. As the incidence of underlying disease was 76.19% and 26.34%, the rate of moderate to high pulmonary involvement was 15.88% and 10.27%, and rate of SpO2 less than normal value were 88.89% and 71.88%, respectively among elderly and others. These observations explained the statistically significant negative association between age and utility values. As age increases, COVID-19 disease utility value dramatically falling. This value was 0.917 and 0.714 for the youth and elderly, respectively. This means that COVID-19 detriment 8.3% and 28.6% of HRQoL for these two age groups, respectively. Other studies have confirmed higher morbidity and mortality among elderly patients compared with others[24, 25]. This explanation is also correct for the variable of having underlying diseases. Respondents with underlying diseases showed statistically significantly higher severe symptoms, hospitalization rates in the ICU, and severe lung involvement than their counterpart’s whiteout underlying diseases. Therefore, both age and underlying disease factors can be introduced as confounding variables in our analysis.
COVID-19 disease in terms of a detrimental effect on HRQoL among survivors of diseases is comparable with Crohn's disease, ulcerative colitis , thalassemia patients that receive oral iron chelator , rheumatoid arthritis  and chronic eustachian Tube dysfunction . All of these diseases lead to the loss of 15–17% of patients' HRQoL. However, it should be noted that the burden of COVID-19 disease is not comparable to the diseases mentioned above, because COVID-19, unlike others, is an acute disease and has a much higher mortality rate.
As far as we know, this study, for the first time, calculated and presented the utility value of COVID-19 disease, which has very fundamental applications in the burden of disease and economic evaluation studies. To calculate the disease burden, we must calculate the indexes of years of life lost due to premature mortality (YLL) and years lived with disability (YLD), separately. Utility value for the YLL will be zero, but for YLD, we can apply the obtained overall mean (median) value for different health states in this study.
Besides, in cost-effectiveness studies on COVID-19 disease, researchers need to know the health states and associated health utility values. Based on the findings of the univariate and multivariate analysis models, it is recommended that the patient's hospitalization status (non-hospitalized, general wards hospitalized, ICU hospitalized, and intubated) be used as a reliable proxy to express the severity and grading of COVID-19 disease. Because of the disease's symptoms and complications have significant variations in different patients, the same criteria cannot be considered for all[31, 32]. Nevertheless, the patient's hospitalization status can represent all effects of COVID-19 disease. The post-hoc analysis confirmed that the mean (median) of utility values obtained for each of the four conditions has a statistically significant difference compared with its higher-grade at 0.01 significant level.
Multi-centeredness and a have a sufficient sample size in the different health states were strengths of the study. However, the findings of the study should be interpreted in light of its limitations. First, we invited the most literate persons of the family for the interview as a proxy, instead of subjects below 15 years old, which constitute 6.2% (18 persons) of the total participants. This sample selection strategy could lead to the over-estimation of the disease utility value because the mean (median) value of the disease utility was 0.966 (0.993) and 0.856 (0.904) for patients younger and older than 15 years, respectively. Second, due to the impossibility of face-to-face interviews with the participants due to the prevention of possible transmission of the disease to the interviewer, the telephone interview may have affected the responses of the participants. Third, while the respondents were newly treated from the disease, the study's clinical findings can only be generalized to the survivors. The severity of the disease among treated participants could be significantly lower than the whole patients.