Usefulness of the ILD-GAP index in predicting COVID-19 pneumonia prognosis

Abstract

Introduction: side the high mortality level of COVID-19 during the acute phase, we still lack estimation of its long term mortality.Since COVID-19 can be considered as an acute interstitial lung disease(ILD) because of similar radiological lesions, ILD-GAP index which is derived from GAP score to be applicable to all ILD subtypes could be used to evaluate COVID-19 pneumonia long term mortality.

Aim: Evaluate COVID-19 long term mortality using ILD-GAP index and look for its eventual correlations with acute phase parameters.

Methods: Our study included 38 COVID-19 diagnosed patients after about two months of discharge. Clinical data, spirometry, DLCO and 6-minute walk test (6-MWT) were analyzed.

Results: Our population had a median age of 60 years (20-83), a sex-ratio of 1,4 and a BMI of 30,3kg/m2 (20-83). Median values were  85% (48-124) for FVC and 78% (35-112) for DLCO. The ILD-GAP index was 0-1 in 91.1% and 2-3 in 8.1% of study population. This index was positively correlated to both hospitalization duration (p=0,004; r=0,263), oxygenotherapy duration(p=0,015; r=0,397) and maximal oxygenotherapy volume needed (p=0,048; r=0,327). However, this index was negatively correlated to % of FEV1 (p=0,002; r=-0,494) and static volumes: RV(p=0,021;r=-0,408), FRC (p=0,024;r=-0,398) and TLC (p=0,009 ;r=-0,422).We also found ILD-GAP to be negatively correlated to 6-DWD (p<0,001;r=-0,569) and  final % of SaO2 (p<0,001;r=-0.643) during 6-MWT.

Conclusion: The correlations found between the ILD-GAP index and several clinical and functional parameters confirm its usefulness to predict prognosis of COVID-19 pneumonia.These results could also justify closer monitoring of patients with a high ILD-GAP index after COVID-19 pneumonia.