Organophosphate (OP) poisoning represents a significant global health challenge, accounting for approximately 3 million poisoning cases annually and 300,000 deaths, predominantly in developing countries.[1] The World Health Organization estimates that pesticide poisoning contributes to about one-third of global suicides, with organophosphates being the most commonly used agents.[2] This high mortality rate, coupled with the widespread availability of these compounds, makes OP poisoning a critical public health concern requiring prompt diagnosis and accurate severity assessment for optimal management.

Organophosphates exert their toxic effects primarily through the inhibition of acetylcholinesterase (AChE), leading to the accumulation of acetylcholine at synaptic junctions.[3] This accumulation results in the characteristic clinical manifestations of cholinergic excess, affecting multiple organ systems through muscarinic, nicotinic, and central nervous system effects. The traditional approach to assessing OP poisoning severity has relied heavily on clinical parameters and cholinesterase levels. However, these methods have several limitations, including the subjective nature of symptom evaluation, variable presentation patterns, delayed onset of certain manifestations, and limited availability of cholinesterase assays in resource-constrained settings.

Recent research has focused on identifying alternative biomarkers that could provide more reliable and objective assessment of poisoning severity.[4] Among these, serum amylase and creatine phosphokinase (CPK) have emerged as promising candidates. Serum amylase reflects pancreatic involvement and may indicate cholinergic overstimulation, while CPK reflects muscle injury and rhabdomyolysis, indicating the severity of nicotinic effects. The relationship between these enzymatic markers and OP poisoning severity has been documented in various studies, with research suggesting they may serve as early warning indicators of severe clinical manifestations. [5-7] This study aims to evaluate the comparative utility of serum amylase and CPK levels in assessing OP poisoning severity, potentially establishing more reliable and objective criteria for severity assessment and prognostication.

This prospective cohort study was conducted at Shri B M Patil Medical College Hospital and Research Centre, Vijayapura, from May 2023 to December 2024. A sample size of 73 patients was calculated based on previous studies showing the proportion of severity of OP poisoning according to the POP scale as 5%, with a confidence limit of 95%, a 5% level of significance, and a margin of error of 0.05.

The study included patients above 18 years of age who were admitted with organophosphate poisoning. Patients with a history of organophosphate compound consumption mixed with alcohol or other poison and those with comorbid conditions like chronic alcoholism, musculoskeletal, hepatic, and renal disease were excluded.

At admission, detailed history was collected according to a pre-designed proforma. Clinical examination was performed, and the severity of poisoning was assessed using the Peradeniya Organophosphorus Poisoning (POP) scale. The POP scale evaluated six clinical parameters (pupil size, respiratory rate, heart rate, fasciculation, level of consciousness, and seizures) on a three-point scale (0-2 points each). The total score was calculated by adding individual parameter scores, with severity graded as mild (0-3), moderate (4-7), and severe (8-11).

Blood samples were collected for various investigations including complete blood count, renal function tests, liver function tests, serum cholinesterases, serum amylase, and creatine phosphokinase levels. The serum amylase and creatine phosphokinase levels were measured on days 1, 3, and 5 of admission along with the POP score assessment. Written informed consent was obtained from all participants after explaining the study procedure in detail. The study protocol was approved by the institutional ethics committee of the hospital.

Statistical analysis was conducted using SPSS version 20. The mean, standard deviation, counts, and percentages were used to display the results. An independent sample test was employed for continuous variables that were normally distributed between two groups. For variables that weren't normally distributed, the Mann-Whitney U test was used. Fisher's exact test or the Chi-square test were used to compare categorical variables between two groups. ANOVA for normally distributed data and the Kruskal-Wallis H Test for non-normally distributed data were employed for comparisons involving more than two groups. Statistical significance was defined as a p-value of less than 0.05.

Demographic and Clinical Characteristics

A total of 73 patients with organophosphate poisoning were included in the study. Table 1 shows the demographic and clinical characteristics of these patients.

Table 1: Demographic and Clinical Characteristics of Patients with Organophosphate Poisoning

The mean time since exposure to hospital presentation was 5.9 ± 4.5 hours. The mean pupil size was 2.1 ± 0.84 mm, suggesting miosis (pupillary constriction). The mean length of hospital stay was 5.45 ± 3.2 days. Ventilatory support was required in 26% of patients, and the overall mortality rate was 15.1%.

Biochemical Parameters and Correlation with Severity

Table 2 shows the distribution of acetylcholinesterase enzyme levels, serum amylase, and CPK at different intervals and their correlation with severity.

Table 2: Distribution of Biochemical Parameters and Correlation with Severity

Significant associations were observed between severity grading and biochemical parameters. Mean amylase levels were 92.6 ± 13.8 units in mild cases, 161.8 ± 24.3 units in moderate cases, and 251.7 ± 29.3 units in severe cases (p<0.001). Similarly, mean CPK levels were 73.6 ± 13.2 units in mild cases, 110.6 ± 19.7 units in moderate cases, and 308.1 ± 63.1 units in severe cases (p<0.001).

Association of Biochemical Parameters with Severity and Outcome

Table 3 illustrates the association of acetylcholinesterase enzyme levels with severity, biochemical parameters, and outcomes.

Table 3: Association of Acetylcholinesterase Enzyme Levels with Severity, Biochemical Parameters, and Outcomes

A significant association was observed between acetylcholinesterase levels on admission and patient outcomes. Among patients with enzyme levels <5320 units, 34.5% were non-survivors, compared to only 6.7% among those with levels >5320 units (p=0.034).

Table 4 presents the association of severity grading with biochemical parameters on day 1.

Table 4: Association of Severity Grading with Biochemical Parameters on Day 1

These findings demonstrate a significant association between biochemical parameters and clinical severity, with strong correlations between the POP score and both amylase (r=0.865, p<0.001) and CPK levels (r=0.817, p<0.001), suggesting their potential utility as severity markers in organophosphate poisoning.

Our study demonstrates that organophosphate poisoning predominantly affects young adults, with 67.1% of cases occurring in the 21-40 years age group. This finding aligns with previous studies by Banday et al., who reported that 70% of cases in their study were between 21-40 years of age, suggesting that the economically productive age group is most vulnerable to such exposures.[8] The gender distribution in our study was nearly equal, with a slight female predominance (50.7% vs. 49.3%), which differs somewhat from other studies such as that by Muley et al., who reported a male preponderance (63% males vs. 37% females) in their study of 90 OPP cases.[9] The almost equal gender distribution in our study could be attributed to regional variations in agricultural practices, socioeconomic factors, and cultural norms that influence access to and handling of pesticides.

Regarding clinical presentation, vomiting was the most common symptom (76.7%), followed by muscle weakness (37%), bronchospasm (31.5%), and diarrhea (23.3%). This constellation of symptoms aligns with the cholinergic excess characteristic of organophosphate poisoning. Similar findings were reported by Banday et al., who observed vomiting in 78% of cases, followed by salivation (65%) and fasciculations (48%).[8] According to the POP scale, 43.8% of patients were classified as having mild poisoning, 39.7% as moderate, and 16.4% as severe. This distribution is comparable to that reported by Rehiman et al., who found 42% mild, 38% moderate, and 20% severe cases in their study of 50 patients.[10] We observed a significant association between acetylcholinesterase levels and severity grading based on the POP scale. Mean acetylcholinesterase levels on day 1 were 4526.1 ± 3396.8 units in mild cases, 3136.4 ± 2731.6 units in moderate cases, and 1671.3 ± 2136.6 units in severe cases (p=0.005). Furthermore, our study revealed a significant association between acetylcholinesterase levels on admission and patient outcomes, with higher mortality rates (34.5% vs. 6.7%, p=0.034) among patients with lower enzyme levels (<5320 units).

Our study found elevated serum amylase levels (>110 units) in 63% of patients on day 1, similar to findings by Singh et al., who reported elevated serum amylase in 66% of their patients.[11] Mean amylase levels were 92.6 ± 13.8 units in mild cases, 161.8 ± 24.3 units in moderate cases, and 251.7 ± 29.3 units in severe cases (p<0.001), demonstrating a robust correlation (r=0.865, p<0.001) between serum amylase and clinical severity. Elevated CPK levels (>200 units) were noted in 16.4% of patients on day 1, with mean CPK levels of 73.6 ± 13.2 units in mild cases, 110.6 ± 19.7 units in moderate cases, and 308.1 ± 63.1 units in severe cases (p<0.001), showing a strong correlation (r=0.817, p<0.001) with clinical severity. Similar findings were reported by Bhattacharyya et al., who found significantly higher CPK levels in moderate and severe poisoning compared to mild cases.[12] While both markers showed significant correlations with clinical severity, amylase demonstrated a slightly stronger correlation compared to CPK, suggesting its potential value as a slightly more reliable marker for severity assessment. This finding is particularly relevant in resource-constrained settings where acetylcholinesterase assays may not be readily available, as serum amylase is a relatively simple and widely available test that could provide valuable prognostic information to guide clinical management.

Serum amylase and CPK levels demonstrate strong correlations with clinical severity in organophosphate poisoning, with amylase exhibiting a slightly stronger correlation. These readily available biochemical markers can serve as valuable adjuncts to clinical assessment in determining severity and predicting outcomes, particularly in settings where acetylcholinesterase assays are not available. The significant associations between these markers and patient outcomes highlight their prognostic value, with patients having markedly elevated amylase or CPK levels possibly warranting closer monitoring and more aggressive management due to their higher risk of developing complications. Future research with larger sample sizes is warranted to establish definitive cut-off values for these markers in clinical decision-making, which could potentially enhance the management of organophosphate poisoning cases, particularly in resource-constrained settings.

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