Characteristics and Risk Factors of Persistent Neuropathic Pain in Recovered COVID-19 Patients.

Objectives: To assess risk factors for persistent neuropathic pain in subjects recovered from coronavirus disease 2019 (COVID-19) and to study the serum level of neurofilament light chain (NFL) in those patients.

Design: Case-control study.

Setting: Persistent post-COVID-19 pain.

Subjects: In total, 45 patients with post-COVID-19 pain and another 45 age and sex-matched healthcare workers who recovered from COVID-19 without pain.

Methods: The included participants were subjected to medical history taking, screening for depressive disorders, comprehensive neurological examination, and pain evaluation using the Douleur Neuropathique en 4 questions (DN4). All patients who had a score at least 4/10 on DN4 were included. The serum NFL level was measured for both groups at the time of patients' enrollment.

Results: The frequency of depression, moderate and severe COVID-19 cases, disease duration and serum ferritin were significantly higher in the cases with post-COVID-19 pain than controls. Binary logistic regression revealed that depression, azithromycin use, moderate and severe COVID-19 increased the odds of post-COVID-19 pain by 4.462, 5.444, 4.901, and 6.276 times, respectively. Cases with post-COVID-19 pain had significantly higher NFL (11.34 ± 9.7, 95% confidence interval [CI]: 8.42-14.25) than control group (7.64 ± 5.40, 95% CI: 6.02-9.27), (P value = .029). Patients with allodynia had significantly higher NFL (14.96 ± 12.41, 95% CI: 8.58-21.35) compared to those without (9.14 ± 6.99, 95% CI: 6.43-11.85) (P value = .05).

Discussion: Depression, azithromycin, and moderate and severe COVID-19 are independent predictors of persistent post-COVID-19 pain. Serum NFL may serve as a potential biomarker for persistent neuropathic pain after COVID-19.