The relationship of serum amylase levels in acute organophosphorus poisoning with its clinical severity and outcome: a cross-sectional study

Background: There are limited literatures studying the pancreatic involvement in organophosphate (OP) poisoning using biochemical means. This study focused on assessing the type of OP poisoning and determining the association of serum amylase levels with the patient’s presentation and outcome. Materials and methods: A cross-sectional study was carried out in the Maharajgunj Medical Campus, Tribhuwan University Teaching Hospital, Kathmandu, Nepal, after ethical approval [Ref: IRB/308 (6-11-E)]. We collected data from 172 participants with OP poisoning over the period of 2 years using nonprobability purposive sampling method. All patients with age group 16–75 years having a history of OP poisoning within the previous 24 h with clinical features and physical evidence of poisoning were included in the study. Those participants with indications of exposure to an entirely different poisons, poisoning with multiple poisons, OP poisoning along with alcohol, chronic alcoholics, comorbid conditions, taking drugs that could affect serum amylase levels (azathioprine, thiazides, furosemide, etc.), and/or treated in other hospitals after poisoning were excluded from the study. Appropriate statistical calculations were made using the statistical package for social sciences (SPSS), version 21. The P-value of less than 0.05 was considered statistically significant. Results: Metacid (53.5%, 92) was the most common OP poison. There were significantly higher mean values of serum amylase levels either within 12 h of exposure (468.60 vs. 135.4 IU/ml, P<0.001) or after 12 h of exposure (152.0 vs. 58.9 IU/ml, P<0.001) in dead participants than alive ones. The participants with initial and after 12 h of exposure-serum amylase level 100 or more IU/ml had more than two-fold and 18-fold higher odds of severe/life-threatening severity (odds ratio=2.40, 95% CI: 1.28–4.52, P=0.007 and odds ratio=18.67, 95% CI: 8.02–43.47, P<0.001) respectively than those with less than 100 IU/ml. Conclusions: The clinical severity of OP poisoning is directly related to serum amylase levels. Importantly, higher mean values of serum amylase levels were depicted in those participants with OP poisoning culminating to death. Thus, serum amylase level could be one of the easy measurable prognostic marker of OP poisonings.


Introduction
One of the commonest poisonings, that is, acute OP poisoning has attained epidemic proportion in most parts of the world. The toxicity of OP poison and lack of medical management especially in developing countries has led to its high fatality rate [1,2] . The incidence of OP as a self-poison is higher in younger active groups owing to their ease of access and sociocultural factors [3] .
Acute pesticide poisoning is a universal public health problem and accounts more than 0.3 million deaths [4] . The OP compounds hold a major proportions of inpatient deaths among poisoning cases in Nepal [5,6] . Thus, early recognition and timely HIGHLIGHTS • The most common organophosphate (OP) compound used for poisoning is Metacid. • Serum amylase could be an important prognostic marker of OP poisoning. • This study demonstrated higher mean values of serum amylase levels among severe/life-threatening participants with OP poisoning. • Higher mean values of serum amylase levels in participants with OP poisoning who became dead in the course of treatment suggests the outcome of participants could be gauzed based on serum amylase levels.
intervention of toxicity from these compounds are of paramount importance. Case reports on acute pancreatitis following acute OP ingestion has been reported now and then, but appropriate literature with reference to the pancreatitis is not available. Hence, we attempted to study pancreatic involvement in OP poisoning biochemically. Although we came across a large number of patients with this poisoning now in our clinical practice, there was no local literature available regarding the frequency of high amylase levels. In the study from India by Patil et al. [7] , hyperamylasemia was seen in all the cases with OP poisoning. This study was therefore designed to determine the type of OP used for poisoning and to assess the relationship of serum amylase levels with a patient's presentation and outcome. Since the national prevalence of OP poisoning was not available, 1-month emergency medical record was reviewed and the prevalence of OP poisoning was found to be 0.5% (17 August-16 September 2016). Assuming the prevalence of OP poisoning to be 0.5% with a significance level set at 5%, absolute precision of 1.05%, and a finite population correction, the sample size was computed to be 172. The nonprobability purposive sampling method was adopted for data collection. All patients with the age group 16-75 years having a history of OP poisoning within the previous 24 h with clinical features and physical evidence of poisoning were included in the study. Those participants with indications of exposure to an entirely different poison other than OP poison, poisoning with multiple poisons, OP poisoning along with alcohol, chronic alcoholics, comorbid conditions, taking drugs that could affect serum amylase levels (azathioprine, thiazides, furosemide, etc.), and/or treated in other hospitals after poisoning were excluded from the study. Bardin's classification was adopted for gauzing the severity of the patients with OP poisoning [8,9] . Based on this, we categorized OP poisoning patients into either mild or severe/life-threatening groups. Mild OP poisoning groups included those with a history of exposure/intake with mild signs like normal consciousness, mild secretions, and little fasciculations. Similarly, severe/lifethreatening OP poisoning patients included those with a history of intake/exposure with severe signs like altered consciousness, copious secretions, generalized fasciculations, suicide efforts, partial pressure of oxygen less than 75 mmHg, and abnormal roentgenogram. At least two criteria were required to grade. If fewer criteria are present, then the previous grade was used. This work has been registered with UIN researchregistry8675 and carried out in accordance with the STROCSS criteria [10] . The ethical clearance was obtained from the Institutional Review Committee of Maharajgunj Medical Campus, Tribhuwan University Teaching Hospital, Kathmandu, Nepal.

Data entry and analysis
The data gathered were tabulated in Microsoft excel 2019, v16.0 (Microsoft), and analysis was carried out using the statistical package for social sciences (SPSS), version 11.5 (IBM SPSS, v22; IBM Corp.). Descriptive statistics like mean, SD, range, and/or percentages were used to present data like background characteristics and characteristics of poisoning products. The chisquare test was used to check the association between categories of initial and 12 h postexposure amylase levels with the patient's severity. For binary logistic regression, odds ratio (OR) and 95% CI was calculated. For comparing mean serum amylase level between alive and dead patients within and after 12 h of exposure, an independent sample t-test was used. The P-value of less than 0.05 was regarded as statistically significant.

Results
Of the 172 respondents, the mean age of participants was 34.6 14 years. The majority of the participants belonged to the age group 15-24 years (29.1%, 50) followed by 25-34 years (26.7%, 46). Similarly, the majority of the participants were female (74.4%, 128), and takes 30 min or more to reach the nearby hospital (74.4%, 129). About one-third of the participants (34.9%, 61) sought for help. The most common reason for poisoning was suicidal (97.7%, 168) ( Table 1).
The participants with initial serum amylase (within 12 h of exposure) level 100 IU/ml or more had more than two-fold higher odds of severe/life-threatening severity (OR = 2.40, 95% CI: 1.28-4.52, P = 0.007) than those with less than 100 IU/ml. Similarly, the participants with serum amylase 100 IU/ml or more after 12 h of exposure had more than 18-fold higher odds of severe/life-threatening severity (OR = 18.67, 95% CI: 8.02-43.47, P < 0.001) than those with less than 100 IU/ml (Table 3).
Of 172 participants, about 9.3% became dead in the course of treatment. The dead participants had significantly higher mean values of serum amylase levels either within 12 h of exposure (468.60 vs. 135.4 IU/ml, P < 0.001) or after 12 h of exposure (152.0 vs. 58.9 IU/ml, P < 0.001) than alive participants (Table 4).

Discussions
In our study, patients with initial (within 12 h) and after 12 h of OP poison exposure had more than two-fold and 18-fold higher odds of severe/life-threatening presentations, respectively. In a study from Iran by Zobeiri [11] , the rise in plasma amylase, more than 60% above the normal upper limit on the admission time was associated with clinical severity and mortality following OP poisoning. In a study by Patil et al. [7] , from India, amylase levels was raised in all the OP poisoning cases, and the significantly higher mean value of serum amylase was noted in those who became dead than being discharged home. Our study is also consistent with other studies demonstrating that the serum amylase levels rises in OP poisoning and predicts the severity [12][13][14] . Therefore, the serum amylase level in OP poisoning is an easy measurable prognostic marker of OP poisoning [11,15] . The possible explanation for the rise in serum amylase in OP poisoning is a pancreatic injury on account of parasympathetic overstimulation and hypersecretion [14,16] . In human body, two major organs like pancreas and salivary glands account for the majority of the serum amylase level activity. So, hyperamylasemia is seen in states involving the pancreas and salivary glands.
In OP poisoning, besides hyperamylasemia, there could be many biochemical abnormalities like leukocytosis which could be used for diagnosing and managing the cases [17,18] . The OP poisons work by inhibition of cholinesterase enzyme. Henceforth, the estimation of acetylcholinesterase and butyrylcholinesterase are validated screening tools for the diagnosis and prognosis of OP poisoning [19] . Similarly, another potential prognostic indicator in OP poisoning is creatine phosphokinase levels [20,21] . The serum creatine phosphokinase levels could rise due to rhabdomyolysis or intermediate syndrome of OP poisoning [22] .
Our study demonstrated higher mean values of serum amylase level either within 12 h of exposure or 12 h postexposure in participants who became dead during the course of treatment. This shows the serum amylase levels dramatically rises in severe/ life-threatening presentations with OP poisoning which is evident from multiple other studies [11,15,22,23] .
In our study, among the organophosphorus poisoning, the majority (74%) of the participants with OP poisoning were female. The study by Dash et al. [24] , Hussain et al. [25] , and Ahmed et al. [26] demonstrated a higher prevalence of OP poisoning in male than females. However, one study have demonstrated a higher preponderance of OP poisoning in female than male [27] . The sex-based predominance of poisoning could differ from place to place, availability of poisons, and multiple factors surrounding them.
In our study, most of the patients (65%) patient did not call for any help and the majority had taken poison for the suicidal purpose (98%). Studies have depicted that suicidal and occupational poisoning to be more common in agricultural workers of developing countries and accidental OP poisoning to be more common in developed countries [26,28,29] . As agriculture is the main occupation in developing countries like Nepal, pesticides are easily available in lethal and concentrated forms [30] . In our study, ingestion (97%) was the commonest route of poisoning   which is common for OP poisoning and are evident from other study [29] . Our study has also some limitations owing to its crosssectional nature. We could not figure out the causes of suicidal OP poisoning. We have not studied about the mechanical ventilation and ICU admission effect on serum amylase levels. Thus, a better study design would be required to assess the rise in serum amylase levels with a time of onset of exposure to poison after minimizing the confounding factors. Similarly, a study involving a serial measure of serum amylase following OP poisoning and subsequent mechanical ventilation and/or ICU admission would be of paramount importance.

Conclusions
The clinical severity of OP poisoning is directly related to serum amylase levels. Importantly, higher mean values of serum amylase levels were depicted in those participants with OP poisoning culminating to death. Thus, serum amylase level could be one of the easy measurable prognostic marker of OP poisonings. Awareness and regulations must be made for its storage and distribution gave the easy route of exposure and higher predominance of suicidal poisoning, especially in young individuals.

Ethical approval
The ethical clearance was taken from the institutional review board, Maharajgunj Medical Campus, Tribhuwan University Teaching Hospital, Kathmandu, Nepal [Ref. 308 (6-11-E)]. Written informed consent was taken from each participant and the participation was entirely voluntary.

Consent
Witten informed consent obtained.

Sources of funding
None.