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Introduction: COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This emerging disease has become a public health emergency worldwide.

Acute Kidney Injury (AKI) secondary to COVID-19 has been described in different studies, but information characterising patients with subsequent AKI is limited. The cause of kidney involvement in COVID-19 is thought to be multifactorial. Cardiovascular comorbidity and predisposing factors (e.g. sepsis and nephrotoxins) are considered as important contributors. The tubular damage has been linked to the cytopathic effects of kidney-resident cells and cytokine storm syndrome. To gain better understanding of the effect of COVID-19 on renal function, large clinical and register based studies have been requested.

The objective of this study was to quantify the risk of acute kidney injury during and after covid-19.

Methods: This was a Swedish prospective cohort study where Generalised Estimating Equation methods (GEE) was used to map the kinetics of kidney injury markers such as serum-creatinine (s-creatinine), cystatin and eGFR for the hospitalised patients in the cohort, comparing patients with moderate and severe COVID-19 during and after the acute infection. Furthermore, we will investigate if patients with kidney dysfunction during COVID-19 have more severe disease outcome compared with the whole cohort, adjusting for age, sex, and comorbidities. We will also compare start values of kidney injury markers with the latest values and count the percentage worsening among all disease severity groups.

Cohort: Approximately 550 COVID-19 patients were recruited to the study following informed and signed consent at 2 Swedish University Hospitals. A case report form was filled in at pre-specified time points, and samples collected consecutively. A database was then created containing dates and information regarding symptoms, laboratory samples, complications, and disease severity (e.g., need of oxygen, intensive care, mechanical ventilation, death).

Results: There was a significant increase in s-creatinine among hospitalised and intensive care unit patients (n=126) during the acute phase of COVID-19 (day 0-6 post disease onset) when compared to the follow up samples after 90 days from disease onset. There was also a decrease in s-creatinine in day 11-21 and 31-70 among hospitalised and intensive care unit COVID-19 patients when compared to the same follow up samples. This analysis was adjusted for age and sex. See figure 1.

Conclusions: Our preliminary results show that s-creatinine was increased during the first days of COVID-19 followed by decreased levels compared to baseline.

The higher levels of s-creatinine day 0-6 of COVID-19 could be an effect of the acute infection, but it could also be caused by other factors such as dehydration or medication. The lower levels of s-creatinine might be caused by dietary changes or loss of muscle mass due to immobilisation during hospitalisation. Knowledge about fluctuations in s-creatinine in COVID-19 patients may be of use for treating physicians.