Serum KL-6 as a biomarker to assess risk of worse outcome in patients with SARS-CoV2 infection

Abstract

Introduction: SARS-CoV2 infection is associated with an extremely variable disease course. Direct damage of type II pneumocytes is suspected to play a role in mediating and perpetuating lung damage. Serum KL-6, a lung epithelial mucin, is an established marker of interstitial pneumonia (IP).

Objectives: To investigate a possible role of serum KL-6 levels as a biomarker to predict outcome in patients with SARS-CoV2 infection.

Methods: Consecutive patients admitted at Emergency Department with SARS-CoV2 infection were included and followed. Infection was confirmed by RT-PCR test. The WHO Ordinal Scale for Clinical Improvement (0-8 points) was used to classify the clinical course. Serum samples were collected at admission and KL-6 was measured by using automated CLIA immunoassay (Fujirebio). Upper limit of normal was set at 486 U/mL based on previous measurement in our laboratory.

Results: 158 patients (97 M, 61 F, age 61±16 years) were included. 38 patients (87%) developed pneumonia, 63 (40%) requiring NIV, IV or ECMO. 15 (9%) of them died during hospitalisation. Mean Serum KL-6 level at admission was 566±45 U/mL (range:125-5822 U/mL). Patients requiring NIV, IV or ECMO had significantly higher serum KL-6 levels at admission compared to those with mild disease (748±81 vs 386±25, respectively, p<0.0001). A significant correlation between serum KL-6 levels and WHO-outcome scale score was observed (r=0.541, p=0.0002). Serum KL-6 levels were tendentially higher in patients who died than in those who survived (710±142 vs 553±47, respectively).

Conclusions: Serum KL-6 seems to be a useful biomarker to stratify patients with SARS-CoV2 infection for risk of worse disease outcome at admission.