Mean Platelet Volume Lymphocyte Ratio: Could It be a Game-Changer for Early Detection of Diabetic Nephropathy? - a Diagnostic Test Study

Introduction Diabetic nephropathy (DN) causes end-stage kidney disease in 40% of diabetics, often without early symptoms. This study assesses the mean platelet volume/lymphocyte ratio (MPVLR) as an early DN marker. MPVLR, from routine blood counts, links to inflammation. MPV shows platelet activity, and lymphocytes indicate immune response. Elevated MPV suggests more inflammation. MPVLR could be a quick, safe, and cost-effective early DN diagnostic tool. Objective The primary aim is to assess the diagnostic performance of elevated MPVLR in detecting DN. Specific objectives include determining the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR), and negative likelihood ratio (NLR) of elevated MPVLR in detecting DN. Method We analyzed records of 176 type 2 diabetes patients from Victor Lazarte Echegaray Hospital, Trujillo, Peru (2018-2020). Patients had complete blood counts, 24-hour urine albumin, urine albumin/creatinine ratios, and glomerular filtration rates. We excluded those with incomplete data, blood disorders, cancer, chemotherapy, immunosuppressive treatment, cirrhosis, infectious, cardiovascular, or autoimmune diseases. Our goal was to determine the diagnostic validity of elevated MPVLR (≥3.60) compared to albuminuria/creatinuria ≥ 30 mg/g in DN. Data were processed in Excel and analyzed with EPIDAT 4.2 and SPSS Statistics 26, following ethical principles and approvals. Results Data from 176 diabetic patients were analyzed: 122 (69.3%) had DN, and 54 (30.7%) did not. High MPVLR was noted in 142 (80.7%) patients. Among DN patients, 111 (91.0%) had elevated MPVLR; among non-DN patients, 31 (57.4%) had elevated MPVLR (p<0.001). In the DN group, 93 (76.2%) were aged 60 or older, compared to 28 (51.9%) in the non-DN group (p=0.001). Also, 108 (88.5%) of the DN group had a disease duration of 10 years or more, compared to 24 (44.4%) in the non-DN group (p<0.001). Median age for DN patients was 70 years, and 61.5 years for non-DN patients (p<0.001). Median MPVLR was 4.95 for DN patients, and 3.77 for non-DN patients (p<0.001). Median disease duration was 16.5 years for DN patients, and 9.0 years for non-DN patients (p<0.001). Elevated MPVLR detected DN with 91.0% sensitivity, 42.6% specificity, 78.2% PPV, 67.6% NPV, 1.58% PLR, and 0.21% NLR. The ROC curve area for elevated MPVLR detecting DN was 0.729 (95% CI 0.64-0.81). Key factors associated with DN included MPVLR, age ≥ 60 years, and disease duration ≥ 10 years. Non-associated factors were sex, HDL ≤ 40 mg/dl, LDL ≥ 100 mg/dl, and glycated hemoglobin ≥ 7%. Discussion An index cutoff value of 3.60 (AUC=0.729) was used, yielding a sensitivity of 91.0% and a specificity of 42.6%. Similarly, Kocak et al., in a cross-sectional study of 162 patients in Turkey, found a sensitivity of 71.1% and a specificity of 68.0% for elevated MPVLR in detecting DN with a cutoff value of 3.66 (AUC=0.733), which are very similar to the values in this study. This study found that age and disease duration significantly influence DN progression (p < 0.001). In this study, 68.8% of patients were over 60, with a median age of 70. Among those with DN, 76.9% were over 60 (p < 0.001). DN was more frequent in patients with a diabetes duration of ≥10 years, occurring in 81.8% of patients with a median duration of 16.5 years. Kocak et al. reported a similar median duration of 10 years in DN patients (p < 0.001). MPVLR is used as a diagnostic test for DN because DN is driven by inflammation. The platelet index and lymphocyte count in the CBC indicate inflammatory processes, making MPVLR a marker for early DN detection. This study found elevated MPVLR useful for diagnosing DN. Kocak et al., Bolzu et al., and Hudzick et al. also suggested MPVLR as a potent inflammatory marker. However, limitations include a small number of nephropathy-free patients due to a biased hospital population, leading to high glycated hemoglobin levels and long disease duration. MPVLR's specificity is also affected (42.6%) by other inflammatory conditions. Conclusion The MPVLR is an economical tool for detecting diabetic nephropathy (DN) with high sensitivity and reliable predictive values. Including it in routine screenings allows early diagnosis and timely interventions, preventing severe complications. Given DN's global prevalence, further research is essential to validate these findings and improve diagnostics.