Correlation of MPV/Platelet Count Ratio With Blood Culture Positivity in Late-Onset Neonatal Sepsis: Implications for Nursing Practice

Background: Late-onset neonatal sepsis (LOS) is a major cause of morbidity and mortality. Pathogens damage endothelium and platelets, triggering the release of larger platelets. Purpose: To find an association between mean platelet volume (MPV) and the MPV/platelet count ratio (MPR) as a rapid, inexpensive screening tool for LOS. Methods: Secondary analysis of a sepsis bundle study (Level IV neonatal intensive care unit, January–December 2023) included nonsyndromic newborns >3 days old undergoing sepsis evaluation. Demographics, MPV, platelet count, and culture results were extracted from the electronic medical record. MPV/platelet count ratio was calculated as MPV (femtolitre [fL]) ÷ platelet count (×10 9 /L). Groups were compared by culture status. Receiver operating characteristic analysis determined the optimal MPR cutoff. Results: Of 146 episodes, 33 (22.6%) were culture-positive. The median (interquartile range) gestational age was 30 (28.3–35.5) versus 34.2 (28.4–36.3) weeks ( P = .22) and birth weight 1330 (990–2380) versus 1970 (990–2500) g ( P = .35). Culture-positive infants had higher MPV (9.7 [8.2–10.5] versus 8.8 [8.1–9.7] fL, P = .029) and MPR (0.045 [0.027–0.068] versus 0.031 [0.021–0.048], P = .017). An MPR >0.03 predicted culture positivity with sensitivity 60.6%, specificity 62.5%, positive predictive value 32.3%, negative predictive value 84.3%, likelihood ratio (LR+) 1.62, LR− 0.63, and area under the curve 0.634 (95% CI 0.521–0.747; P = .018). Implication for Practice and Research: MPR > 0.03 is significantly associated with culture-positive LOS and may serve as a simple, rapid adjunctive marker for early diagnosis. Prospective validation is required before routine use.