The CALL Score for Predicting Outcomes in Patients With COVID-19

Abstract

To the Editor—Defining prognosis of patients affected by coronavirus disease 2019 (COVID-19) due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is of utmost importance for planning appropriate setting of care and treatment. Therefore, we read with great interest the article by Ji and colleagues that was recently published in Clinical Infectious Diseases [1]. After exclusion of patients presenting with severe COVID-19 syndrome and by using data records of 208 patients suffering from COVID-19, with mean age ± standard deviation [SD] 44.0 ± 16.3 years, the authors derived and validated a novel score, named CALL, based on 4 variables (C = comorbidity, A = age, L = lymphocyte count, L = lactate dehydrogenase [LDH]) aimed at predicting progression toward clinical deterioration. The CALL score ranges from 4 (absence of comorbidity, age under 60 years, lymphocyte count over 1.0 × 109/L, LDH under 250 U/L) to 13 (presence of comorbidity, age over 60 years, lymphocyte count under 1.0 × 109/L, LDH over 500 U/L). The prognostic power for predicting progression toward clinical worsening, defined as respiratory rate ≥30 breaths/min, resting oxygen saturation ≤93%, paO2/FiO2 ratio ≤300 or requiring of mechanical ventilation, was excellent with an area under the receiver operating characteristic (ROC) curve (AUC) of 0.91 (95% confidence interval [CI ] .86 to .94). Using a cutoff value of 6 points, the authors found positive and negative predictive values of 50.7% (38.9%–62.4%) and 98.5% (94.7%–99.8%), respectively. Therefore, after exclusion of patients requiring immediate intensive care unit admission, we tested the predictive power of the CALL score in an Italian COVID-19 population admitted to hospital from 12 March to 20 April 2020 and consisting of 210 patients, 112 males (53.3%), with mean age 67.3 ± 16.8 years. Of them, 97 patients (46.2%) met criteria for progression to severe COVID-19 syndrome, and 37 patients (17.6%) died. Median CALL score was 10 (IQR 8–12). One hundred and fifty-four patients (73.3%) had comorbidity, 144 (68.6%) were over 60 years, 100 (47.6%) had lymphocyte count under 1.0 × 109/L, and 54 (25.7%) had LDH over 500 U/L. Progression to severe COVID-19 syndrome increased from 27.2% in patients with CALL score ≤6 points to 53.0% in patients with CALL score ≥11 points. The predictive power of the CALL score for predicting progression to severe COVID-19 was low with an AUC of 0.622 (95% CI: .533–.688) (Figure 1). Instead, the predictive power of the CALL score as prognosticator for in-hospital mortality was good (AUC 0.768, 95% CI: .705–.823). In conclusion, in our COVID-19 population the CALL score seems to be a good prognosticator for in-hospital mortality but not for progression to severe COVID-19. Other external validations are warranted. ROC curve showing the predictive power of the CALL score for predicting progression to severe COVID-19. Abbreviations: AUC, area under the ROC curve; CALL, comorbidity, age, lymphocyte count, lactate dehydrogenase; COVID-19, coronavirus disease 2019; ROC, receiver operating characteristic. Potential conflicts of interest. The authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Supplementary materials are available at Clinical Infectious Diseases online. Consisting of data provided by the authors to benefit the reader, the posted materials are not copyedited and are the sole responsibility of the authors, so questions or comments should be addressed to the corresponding author.

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