Serial Serum Creatine Phosphokinase and Lactate Dehydrogenase Levels as Biomarkers of Severity and Intermediate Syndrome in Organophosphorus Compound Poisoning: A Prospective Observational Study.

Background Organophosphorus compound poisoning remains an important cause of morbidity and mortality in agrarian regions. Early identification of patients at risk of worsening toxicity and intermediate syndrome remains challenging. Serum creatine phosphokinase and lactate dehydrogenase may reflect neuromuscular and tissue injury and may therefore assist clinical risk stratification. Methods This prospective observational study included 80 adult patients with mild-to-moderate organophosphorus compound poisoning admitted to a tertiary care teaching hospital between March 2025 and June 2025. Poisoning severity was assessed using a modified Peradeniya Organophosphorus Poisoning (POP)-based clinical score. Serum creatine phosphokinase and lactate dehydrogenase levels were measured at admission, 48 hours, and 96 hours. Associations with poisoning severity and intermediate syndrome were evaluated using the Mann-Whitney U test, correlations with the severity score using Pearson correlation, and discriminative performance using receiver operating characteristic curve analysis. Results The mean age was 26.69 ± 8.70 years, 43 patients (53.8%) were male, and accidental exposure was the predominant mode of poisoning, observed in 60 patients (75.0%). Intermediate syndrome developed in eight patients (10.0%), and three patients (3.8%) died. Serum creatine phosphokinase and lactate dehydrogenase levels were significantly higher in moderate poisoning than in mild poisoning at admission, 48 hours, and 96 hours (all p < 0.001). Patients who developed intermediate syndrome had higher biomarker levels throughout hospitalization, including creatine phosphokinase at admission (1281.88 ± 631.83 vs. 434.32 ± 304.95 IU/L; p = 0.001) and lactate dehydrogenase at 48 hours (1516.88 ± 777.95 vs. 528.47 ± 303.78 IU/L; p = 0.001). Biomarker levels correlated positively with the severity score, with the strongest correlations observed for lactate dehydrogenase at admission (r = 0.852, p < 0.001) and creatine phosphokinase at 96 hours (r = 0.687, p < 0.001). Receiver operating characteristic analysis showed excellent discrimination for moderate poisoning and good discrimination for intermediate syndrome. Conclusions Serial serum creatine phosphokinase and lactate dehydrogenase levels were significantly associated with poisoning severity and intermediate syndrome in mild-to-moderate organophosphorus compound poisoning. These inexpensive and widely available biomarkers may be useful adjuncts to clinical assessment, although they should not replace careful monitoring and validated severity assessment. Mortality-related findings require cautious interpretation because only three deaths occurred.