Serum Creatine Phosphokinase Level as a Prognostic Marker for Organophosphorus Poisoning and Its Correlation With Peradeniya Organophosphorus Poisoning Scale.

Introduction: Organophosphorus (OP) compounds are widely used as insecticides in agriculture. The Peradeniya Organophosphorus Poisoning (POP) scale is a simple and effective system for determining the severity of OP poisoning. An increase in serum creatinine phosphokinase (CPK) levels in OP poisoning can be due to persistent oxidative cellular damage to muscle membranes. Accordingly, this study was conducted to assess the correlation between serum CPK levels and the severity of acute OP poisoning.

Aim: This study aimed to correlate serum CPK and disease severity with respect to the POP scoring scale, pseudocholinesterase levels, the requirement for atropine, and the clinical outcomes of the disease.

Materials And Methods: This observational study involved 60 patients with OP poisoning admitted to a tertiary care setup from September 2018 to August 2020. The patients were clinically assessed and categorized based on the POP scale at the time of admission. Serum CPK values were taken at the time of admission, repeated after 48 and 96 hours, and correlated with clinical outcomes and the POP scale. CPK was measured using the VITROS CPK microslide method, and pseudocholinesterase/butyrylcholinesterase (BChE) was measured using the VITROS cholinesterase microslide method. The data were presented as median interquartile range (IQR). Friedman's two-way analysis of variance by ranks served to compare repeated measures within groups over time, the Mann-Whitney U test served to compare differences between two independent groups, the Kruskal-Wallis test served to compare medians across groups, and the Spearman correlation coefficient served to evaluate relationships among the variables.

Observations And Results: The POP scores revealed that serum CPK levels rose as the degree of poisoning increased. The median (IQR) CPK level at admission in the mild group was 240 (180-360) IU/L, the median in the moderate group was 433 (366-507) IU/L, and the median in the severe group was 1,122 (939-1,235) IU/L. Conversely, as the severity of the poisoning increased, the total atropine required increased, but serum levels of BChE decreased. Serum CPK levels and the POP scale showed a strong positive correlation (Spearman's rho=0.831, p=0.0001). Serum CPK levels and the total atropine requirement were also found to be moderately positively correlated (Spearman's rho=0.311, p=0.016). On the other hand, serum CPK levels showed a strong negative correlation with pseudocholinesterase levels (Spearman's rho=-0.631, p=0.00000007). There was also a strong positive correlation between serum CPK at admission and the duration of hospital stays (Spearman's rho=0.84, p<0.0001). The CPK in the patients who required ventilatory support, 419.5 (243.8-697.2), was higher than in patients who did not require ventilatory support, 386.5 (243.8-545.0), p=0.98. The median (IQR) of the initial CPK levels in the patients who died, 1,288 (1,252-1,292), was significantly higher than in the patients who survived, 378 (238-521) (p=0.0001).

Conclusion: Increased severity of OP poisoning as measured by the POP score, the requirement for higher doses of atropine, reduced levels of BChE, longer hospital stays, a greater need for ventilatory support, and a higher risk of death were associated with elevated serum CPK levels at the time of admission. Therefore, the estimation of serum CPK on admission is advisable in patients with OP poisoning because serum CPK can reliably indicate severity.