Long COVID still undetectable by laboratory value

As part of the RECOVER Initiative, a US study with more than 10,000 participants searched for a suitable value that could be used to reliably detect Long COVID in the blood (‘biomarker’). However, none of the 25 routine laboratory values tested proved to be a suitable biomarker. 

8,746 of the participants had already been infected with the SARS-CoV-2 coronavirus. 21.5 per cent of them reported Long COVID symptoms. Among other things, it was investigated whether the laboratory values of the participants with Long COVID symptoms differed from those without long-term symptoms following infection. However, there were no significant differences found between the two groups.

There was evidence of persistent inflammation in the blood of participants with long-term COVID symptoms. A generally higher number of platelets (thrombocytes) and a higher level of a certain inflammatory marker (hsCRP) were measured. However, these values are not suitable as biomarkers for Long COVID.

Irrespective of Long COVID symptoms, participants with a previous infection with the coronavirus had a higher albumin-creatinine ratio in their urine. This value is associated with kidney function and cardiovascular disease. In addition, participants with previous infection had slightly fewer platelets (thrombocytes) in their blood. In addition, people in this group had a higher long-term blood glucose level (HbA1C), which is also elevated in diabetes. There is already evidence from other studies that infection with the coronavirus can contribute to a higher risk of diabetes. However, the differences compared to participants without prior infection were overall minor. None of the analysed values could be used to detect Long COVID.