Neutrophil-Lymphocyte Ratio and Platelet-Lymphocyte Ratio in ADHD: A Systematic Scoping Review

Neutrophil-lymphocyte and platelet-lymphocyte ratio (NLR, PLR) are easily calculated from routine blood tests and are increasingly being used in research to assess disease severity in inflammatory, infectious, and psychiatric conditions. The goal of this systematic scoping review was to broadly examine the literature on NLR and PLR and attention-deficit/hyperactivity disorder (ADHD).

The PubMed/Medline, PsychInfo, Scopus, Embase, Cochrane Central Register of Controlled Trials, Cumulative Index to Nursing and Allied Health Literature, ClinicalTrials.gov, World Health Organization International Clinical Trials Registry Platform, International Standard Randomized Controlled Trial Number, Google Scholar, Directory of Open Access Journals, and ProQuest databases were searched.

Among the 1542 articles evaluated, 15 were included. Fourteen studies evaluated children and adolescents with ADHD and one study evaluated adults. Study outcomes included the comparison of mean NLR and PLR values between ADHD and non-ADHD groups and the association of NLR and PLR values with measures of ADHD symptom severity. Four studies used receiver operating characteristic (ROC) curves to identify potential cut points for the diagnosis of ADHD. Assessing NLR and PLR is economical and minimally invasive.

Based on the 15 studies reviewed, findings suggest NLR and PLR may be promising biomarkers for ADHD. Additional research is justified to further investigate if routine incorporation of NLR and PLR into research and clinical practice could beneficially impact the diagnosis and treatment of patients with ADHD.