Dear Editor,
It is important that clinicians must be aware of possible overlap of the laboratory-based blood tests in people who use drugs (PWUD) and patients with coronavirus disease 2019 (COVID-19) to avoid overlooking or over-diagnosis of patients.
The most common blood findings of the COVID-19 are lymphopenia (75.9%), leukopenia (31.1%), thrombocytopenia (32.8%), while elevated lactate dehydrogenase (45.9%), aspartate aminotransferase (AST) (24.6%), alanine aminotransferase (ALT) (22.4%), creatinine kinase (CK) (14.7%) and C-reactive protein (CRP) (1, 2). There is also a suggestion that lymphopenia due to decreases in both CD4+ and CD8+ T cells might be a critical factor associated with COVID-19 severity and mortality (3). Overlap of laboratory findings between PWUD and patients with COVID-19 is noticeable and should be considered in the clinical management of patients.
Among COVID-19-infected patients, lymphopenia is the most common finding in the complete blood count (CBC) test (1, 2). Lymphopenia could be an overlapped result among PWUD and COVID-19-infected patients. This may be due to T lymphocyte involvement in drug users owing to the expression of all three kinds of opioid receptors on T cells (4). Lymphopenia can sometimes be seen in cocaine, amphetamine, and opioid users (4-6). Another similar feature in laboratory tests is a finding of eosinopenia, which is a more reliable and specific laboratory predictor of COVID-19 than lymphopenia (7). It is important to know that eosinopenia is seen in opiate addicts during opioid abstinence (8, 9).
The angiotensin-converting enzyme (ACE) II receptor that is highly expressed on alveolar type II epithelial cells and bile duct cells, is also the receptor of COVID-19, causing the high pathogenic capacity of COVID-19 for liver damage with abnormal liver function in almost one-half of patients (10). This is also a common finding among PWUD undergoing methadone maintenance treatment (11). One study revealed that half of the MMT individuals after 24 months exhibited elevated alkaline phosphatase (ALP) levels, abnormal AST, and ALT levels (12). One of the other parameters for the evaluation of patients with COVID-19 is blood oxygen saturation that is low in some patients (13). This symptom could also be seen among smokers (14).
In the presence of COVID-19, clinicians must be aware of the possible overlap of the tests mentioned above in drug users and patients with COVID-19 to avoid overlooking or over-diagnosis of patients.
