Changes in laboratory value improvement and mortality rates over the course of the pandemic: an international retrospective cohort study of hospitalised patients infected with SARS-CoV-2
Authors: Hong Chuan , Zhang Harrison G , L'Yi Sehi , Weber Griffin , Avillach Paul , Tan Bryce W Q , Gutiérrez-Sacristán Alba , Bonzel Clara-Lea , Palmer Nathan P , Malovini Alberto , Tibollo Valentina , Luo Yuan , Hutch Meghan R , Liu Molei , Bourgeois Florence , Bellazzi Riccardo , Chiovato Luca , Sanz Vidorreta Fernando J , Le Trang T , Wang Xuan , Yuan William , Neuraz Antoine , Benoit Vincent , Moal Bertrand , Morris Michele , Hanauer David A , Maidlow Sarah , Wagholikar Kavishwar , Murphy Shawn , Estiri Hossein , Makoudjou Adeline , Tippmann Patric , Klann Jeffery , Follett Robert W , Gehlenborg Nils , Omenn Gilbert S , Xia Zongqi , Dagliati Arianna , Visweswaran Shyam , Patel Lav P , Mowery Danielle L , Schriver Emily R , Samayamuthu Malarkodi Jebathilagam , Kavuluru Ramakanth , Lozano-Zahonero Sara , Zöller Daniela , Tan Amelia L M , Tan Byorn W L , Ngiam Kee Yuan , Holmes John H , Schubert Petra , Cho Kelly , Ho Yuk-Lam , Beaulieu-Jones Brett K. , Pedrera-Jiménez Miguel , García-Barrio Noelia , Serrano-Balazote Pablo , Kohane Isaac ,   The Consortium for Clinical Characterization of COVID-19 by EHR (4CE), South Andrew , Brat Gabriel A , Cai Tianxi 
Published: June 2022

Objective

To assess changes in international mortality rates and laboratory recovery rates during hospitalisation for patients hospitalised with SARS-CoV-2 between the first wave (1 March to 30 June 2020) and the second wave (1 July 2020 to 31 January 2021) of the COVID-19 pandemic.

Design, setting and participants

This is a retrospective cohort study of 83 178 hospitalised patients admitted between 7 days before or 14 days after PCR-confirmed SARS-CoV-2 infection within the Consortium for Clinical Characterization of COVID-19 by Electronic Health Record, an international multihealthcare system collaborative of 288 hospitals in the USA and Europe. The laboratory recovery rates and mortality rates over time were compared between the two waves of the pandemic.

Primary and secondary outcome measures

The primary outcome was all-cause mortality rate within 28 days after hospitalisation stratified by predicted low, medium and high mortality risk at baseline. The secondary outcome was the average rate of change in laboratory values during the first week of hospitalisation.

Results

Baseline Charlson Comorbidity Index and laboratory values at admission were not significantly different between the first and second waves. The improvement in laboratory values over time was faster in the second wave compared with the first. The average C reactive protein rate of change was –4.72 mg/dL vs –4.14 mg/dL per day (p=0.05). The mortality rates within each risk category significantly decreased over time, with the most substantial decrease in the high-risk group (47.1% in March–April 2020 vs 30.8% in November 2020 to January 2021, p<0.001) and a moderate decrease in the intermediate-risk group (21.5% in March–April 2020 vs 14.3% in November 2020 to January 2021, p<0.001).

Conclusions

Admission profiles of patients hospitalised with SARS-CoV-2 infection did not differ greatly between the first and second waves of the pandemic, but there were notable differences in laboratory improvement rates during hospitalisation. Mortality risks among patients with similar risk profiles decreased over the course of the pandemic. The improvement in laboratory values and mortality risk was consistent across multiple countries.