Predictive Value of Platelet Dynamics for Clinical Outcomes in Patients with Dengue Fever: A Retrospective Observational Study

Abstract

Background: Dengue fever presents with evolving haematological alterations, notably progressive thrombocytopenia during the critical phase followed by recovery. While absolute platelet counts are routinely monitored, longitudinal platelet dynamics may offer additional insight into disease progression and hospitalization outcomes.

Objective: To characterize platelet dynamics and evaluate their clinical association with outcomes in hospitalized adult dengue patients, focusing on platelet nadir, timing of nadir, onset of platelet recovery, severity of thrombocytopenia, transfusion frequency, and length of hospital stay (LOS).

Methods: This retrospective observational study evaluated 110 hospitalized adult patients with confirmed dengue fever at Liaquat National Hospital, Karachi (September 2025–February 2026). Demographic, clinical, diagnostic, serial platelet, treatment, and outcome parameters were extracted. Platelet values documented per day of illness were analyzed for nadir, day of nadir, and onset of recovery. Categorical variables were presented as frequencies (%), and continuous variables as mean ± standard deviation (SD) or median (range). Spearman rank correlation was used to assess associations between platelet-dynamic variables and LOS.

Results: Among 110 records, age was available for 100 patients (mean 38.97 ± 17.65 years; range 13–79), and sex for 103 (63.1% male). Common clinical features included fever (97.9%, 94/96), vomiting (41.7%, 40/96), fatigue (24.7%, 23/93), and abdominal pain (21.9%, 21/96). At least one platelet count < 150 × 10⁹/L was observed in 83.6% (92/110) of patients, and < 50 × 10⁹/L in 68.2% (75/110). Mean platelet nadir was 35.93 ± 41.13 × 10⁹/L (median 22; n = 89), occurring at illness day 5.58 ± 1.34 (median 6; n = 90). Platelet recovery began at day 6.98 ± 1.43 (median 7; n = 83). Platelet transfusions were administered in 18.9% (17/90) of cases. Mean LOS was 4.08 ± 1.91 days (range 1–15). Of 93 patients with recorded final outcomes, 92.5% (n = 86) recovered and 7.5% (n = 7) left against medical advice; no deaths occurred. One complication was documented among 92 patients (1.1%). Platelet nadir (ρ = -0.096, P = 0.373), day of nadir (ρ = -0.135, P = 0.207), and day of recovery (ρ = 0.195, P = 0.079) showed no statistically significant correlation with LOS.

Conclusion: Serial platelet monitoring reveals a predictable temporal pattern of decline and recovery during dengue infection. While platelet dynamics serve as meaningful physiological indicators of phase transition, low adverse outcome event rates precluded demonstration of independent predictive value for LOS or complications in this cohort.