Ethical issues in research involving minority populations: the process and outcomes of protocol review by the Ethics Committee of the Faculty of Tropical Medicine, Mahidol University, Thailand.

BACKGROUND: Recruiting minorities into research studies requires special attention, particularly when studies involve "extra-vulnerable" participants with multiple vulnerabilities, e.g., pregnant women, the fetuses/neonates of ethnic minorities, children in refugee camps, or cross-border migrants. This study retrospectively analyzed submissions to the Ethics Committee of the Faculty of Tropical Medicine (FTM-EC) in Thailand. Issues related to the process and outcomes of proposal review, and the main issues for which clarification/revision were requested on studies, are discussed extensively. METHODS: The study data were extracted from proposals and amendments submitted to the FTM-EC during the period October 2009 - September 2012, and then analyzed qualitatively and quantitatively. The main issues for clarification/revision were analyzed by thematic content analysis. RESULTS: 373 proposals were submitted; 44 studies involved minority groups with 21 extra-vulnerable minorities. All clinical and 2/3 of non-clinical studies submitted for initial review underwent full-board review. For combined clinical and non-clinical study submissions, 92.1% were referred back to the investigators and approved after clarification/revision, while 2.7% were deferred due to major/critical changes, and 2.1% not approved due to substantial violations of ethical principles. The main issues needing clarification/revision differed between all studies and those involving minorities: participant information sheet (62.2% vs. 86.4%), informed consent/assent form (51.2% vs. 86.4%), and research methodology (80.7% vs. 84.1%), respectively. The main ethical issues arising during the meetings, regarding studies involving minorities, included ensuring no exploitation, coercion, or pressure on the minority to participate; methodology not affecting their legal status; considering ethnicity and cultural structure; and providing appropriate compensation. CONCLUSION: Delays in the approval or non-approval of studies involving minorities were mainly due to major or minor deviations from acceptable ethical standards and/or unclear research methodology. The FTM-EC has employed several mechanisms in its operations, including transparency in the review process, building good relationships via open communication with investigators, requesting investigators to consider closely the necessity to enroll minority groups and the risk-benefits for individuals and their communities, and the inclusion of minority-community engagement when developing the proposal. Other effective activities include annual study-site inspections, and offering refresher courses to raise awareness of minority and vulnerability issues among researchers.

Knowledge, attitudes, and acceptability of a human papilloma virus vaccine among students, parents and teachers in Thailand.

The purpose of this study was to assess the knowledge and attitudes about human papilloma virus (HPV) and cervical cancer, and the acceptability of HPV vaccine among students, parents and teachers in secondary schools in Bangkok, Thailand. We conducted a school-based cross-sectional study at four public secondary schools in Bangkok. A total of 644 students aged 12-15 years, 664 parents and 304 teachers were recruited into the study. Data were collected by self-administered questionnaires. The percentages of students, parents and teachers who were willing to be vaccinated were 26, 49 and 43%, respectively. Forty-one percent of parents wanted their children to be vaccinated. Students, parents and teachers had a moderate knowledge of HPV, cervical cancer and the HPV vaccine with mean scores of 6.91 (SD = 1.75), 6.82 (SD = 1.88), and 6.70 (SD = 1.89), respectively. The attitudes of students, parents, and teachers were fair with scores of 3.46 (SD = 0.41), 3.52 (SD = 0.43), and 3.46 (SD = 0.47) out of 5, respectively. Twenty-nine percent of students and 36% of parents were willing to pay USD 14.3-28.5 per dose for the quadrivalent vaccine; 33% of teachers were willing to pay < USD 14.3 per dose for the quadrivalent vaccine. This study is the first study to report the knowledge, and attitudes and acceptability of HPV vaccination in Thailand. The findings suggest the willingness to pay was relatively low and related to the price, while knowledge and attitudes regarding the importance of the HPV vaccine were fair particularly among parents and teachers. Greater effort may be needed to educate people regarding the cost and benefits of HPV vaccination before it would be more acceptable to parents, teachers and students in Thailand.

Social factors related to quality of life among HIV infected children in ubon Ratchathani Province, Thailand.

A cross-sectional study was conducted to determine the social factors and quality of life of HIV infected children attending the Pediatric Infectious Disease Clinic, Sappasithiprasong Hospital, Ubon Ratchathani Province, Thailand. Data were collected during October-November 2008, by interviewing caretakers and their children using a structured questionnaire. The children's families were in need of improved social support (84.5%), since community resources provided limited support, such as clothes, food, financial support, consultation, and information. The HIV infected children's quality of life needed improvement (78.7%). The factors associated with quality of life included having others as main caretakers (OR 4.64, 95% CI 1.45-14.78), parental death (OR 4.19, 95% CI 1.55-11.31), age of caregivers above 45 years old (OR 9.52, 95% CI 2.62-34.53), and family income less than THB 5,000 per month (OR 5.25, 95% CI 1.14-23.39). However, on multivariate analysis, only age of caregiver was a significant predictor for quality of life of the child. Children who were cared for by caregivers aged 45 years or above had a better quality of life than those whose caregivers were 20-45 years old (OR 6.32, 95% CI 1.12-35.62). Therefore, to improve quality of life among HIV infected children, age of caregiver is an important factor to be considered. Government and non-government organizations should focus on supporting caregivers in terms of food, financial, and emotional support based on resources available in the community.

Knowledge, attitudes, and acceptability of a human papillomavirus vaccine among healthcare providers.

A cross-sectional survey was conducted to evaluate acceptability, knowledge, and attitude regarding HPV, cervical cancer, and HPV vaccine among healthcare providers working in hospitals located in Bangkok, Thailand. Two hundred nurses and 100 doctors from three government hospitals and one private hospital were recruited. Data collection was done using a self-administered questionnaire. Nurses and doctors knowledge on HPV, cervical cancer, and HPV vaccine was at a medium level. Both nurses and doctors had positive attitude toward HPV, cervical cancer, and HPV vaccine. Approximately 80% of nurses and 63% of doctors agreed on the use of a HPV vaccination. Almost all the nurses and doctors suggested that adolescent aged < or = 18-years-old should be the target group for HPV vaccination. Furthermore, 73% of nurses and 76% of doctors would recommend clients to receive HPV vaccine.

Migrants and malaria risk factors: a study of the Thai-Myanmar border.

The objective of this study was to investigate factors influencing self-reported malaria among migrants living along the Thai-Myanmar border. Songkaria Village, with 1600 inhabitants and 290 households in Sangkhla Buri District, Kanchanaburi Province, was selected for the study due to its intense malaria transmission. One hundred twenty-five households were randomly selected. Household members were interviewed about the history of malaria, socioeconomic status and knowledge and practices in regard to malaria using a structured questionnaire. Of the respondents, 10%, 42%, and 48% belonged to the Thai, Mon, and Karen ethnic groups, respectively. About 40 % of Thai and Karen migrants and almost 30% of Mon migrants reported having suffered from malaria at least once. Multivariate analysis focused on migrants. The results identified three independent factors for previous malaria: a high risk occupation, ie working primarily in the forest [odds ratio (OR), 3.55; 95% confidence interval 1.3-10.0], ability to read Thai [OR, 4.13 (1.5-11.7)], and correct knowledge about malaria symptoms [OR, 5.18 (1.1-23.5)]. Working conditions among migrants played a major role in acquiring malaria. They could not afford to apply additional preventive measures, such as using a mosquito net or repellent to be used while working. The concept of enhancing the environment for migrants to enable them to protect themselves against malaria needs to be examined. Ways and means of improving the economic conditions of migrants should be considered to minimize exposure to the vector.

Gender differences in KAP related to HIV/AIDS among freshmen in Afghan universities.

This cross-sectional study aimed to describe the level of knowledge, perception/ attitude, and practices related to HIV among 1,054 freshmen students in four Afghan universities differences between genders. A probability, two stage sampling method was used. Data were collected by a self administered structured questionnaire. SPSS software was used for data analysis. Descriptive and inferential statistics were performed. Most of respondents were male (72.1%), their average age was 20.1 +/- 2 years, and most were unmarried (93.4%). The majority (90.8%) were aware of HIV but only 28.3% had a good level of knowledge. Around one-third (35.6%) had a positive level of attitude toward HIV. Approximately 30% had at least one risk practice; therefore, they were counted as high-risk behavior group members. Females were statistically more knowledgeable than males, and high-risk behaviors were significantly more prevalent among males; p = 0.01 and p = 0.001, respectively. However, general awareness, and attitude were not statistically different between genders. A considerable proportion of students (14.6%), as compared to peer-countries, were sexually active. A very high level of sharing injecting needles (4.5%) and shaving sets (20.8%) were also reported among informants.

Treatment-seeking behaviors and improvement in adherence to treatment regimen of tuberculosis patients using intensive triad-model program, Thailand.

The aims of this study were to determine tuberculosis patients' treatment-seeking behaviors, to describe knowledge of TB among TB patients, how that knowledge affected their treatment-seeking behaviors, and to develop an appropriate model to strengthen the existing DOTS program. A cross-sectional study was conducted in all government TB clinics in Samut Prakan Province, Thailand during November 2005-May 2006. The triad model, which emphasizes the role of a triad of persons (the healthcare provider, the TB patient, and his/her treatment supporter), can improve patient adherence to TB treatment regimen. The results showed that only about a quarter (27.7%) of TB patients chose the hospitals with TB clinic for first treatment, while others chose alternative healthcare modes, including self-care and purchasing drugs from drugstores. The rate of successful treatment was higher for the experimental group (96.0%) than the control group (84.9%) (p = 0.057). The confirmed cure rate was also significantly higher in the experimental group (95.3% vs 78.9%, p = 0.02). The program could be utilized to strengthen the existing DOTS program.

Avian influenza protection knowledge, awareness, and behaviors in a high-risk population in Suphan Buri Province, Thailand.

Avian influenza (Al) had outbreaks in Thailand from January 2004 to December 2005, which resulted in 22 human cases, and 14 deaths. Three confirmed cases were reported in Suphan Buri Province in 2004, one of whom died. A cross-sectional study aimed to investigate knowledge, attitudes, and practices about AI in Song Phi Nong District of Suphan Buri Province. Most of the respondents had moderate levels of knowledge. Most of their attitudes towards and practices of the prevention and control of AI were also appropriate. However, the peoples' knowledge about major signs and symptoms of AI was limited. The study suggested that those who had received information from media had better attitudes towards and practices of AI prevention and control, compared with those who had not received information from media. Therefore, the media played an important role in improving knowledge, attitudes, and behaviors; but for the better protection from AI, continuing health education will be necessary in Thailand.

Impacts of pesticide use on semen characteristics among rice farmers in Kienxuong District, Thaibinh Province, Vietnam.

This case-control study assessed the effects of pesticide use on semen characteristics among rice farmers of Kienxuong District, Thaibinh Province, Vietnam. Semen samples of 1,036 rice farmers were obtained by manual masturbation and screened at Commune Health Stations. Of these, 156 abnormal semen samples were identified; 314 rice farmers with normal semen were recruited as controls. The semen characteristics (volume, sperm concentration, total sperm count, motility, vitality and morphology) of the cases were considerably poorer than the controls. Factors associated with abnormal semen after adjusting for age, smoking and alcohol drinking by logistic regression were: distance of less than 300 meters from household to rice fields and duration of work over 10 years as a farmer (adjusted OR = 3.16, 95% Cl: 1.97-5.05 and adjusted OR = 3.98, 95% Cl: 2.20-7.21, respectively). Rice farmers without personal protective equipment (PPE) when spraying pesticides and without pesticide training (adjusted OR = 3.05, Cl: 1.92-4.85 and adjusted OR = 1.90, Cl: 1.14-3.16, respectively) were also at risk for abnormal semen compared to controls. These findings showed the strength of association between pesticide use and abnormal semen characteristics among rice farmers in Kienxuong District, Thaibinh Province, Vietnam.

Reduction of low back muscular discomfort through an applied ergonomics intervention program.

An applied ergonomics intervention program (AEIP) was conducted with male employees who work in the pressing and storage sections of a metal auto parts factory in eastern Thailand. The objective of this study was to reduce worker muscular discomfort at the low back. The study design was a participatory research approach, with quasi-experimental pretest-posttest, and with a non-equivalent control group. Thirty-five persons participated in the AEIP (AEIP group) and 17 persons did not (non-AEIP group). The AEIP was composed of three major categories: (1) top management support; (2) equipment designed for workstations and manual material handling; and (3) administrative intervention, training, and health education. Muscle activity was measured by surface electromyography of the left and right erector spinae, and multifidus muscles; and evaluated by multivariate test for dependent samples (paired observation) and for independent samples. After the AEIP, the low back muscular loads of the AEIP group was significantly reduced, while those of the non-AEIP group were not. Comparison of the means of percentage maximum voluntary contractions (% MVC) of low back muscular activity between the AEIP group and non-AEIP group indicated that the AEIP group had significantly reduced low back muscular load, with a 95% confidence level (p-value < 0.05).

Community-based approach for prevention and control of dengue hemorrhagic fever in Kanchanaburi Province, Thailand.

An action research design was conducted in two villages of Mueang District, Kanchanaburi Province to assess the effectiveness of a community-based approach program. Knowledge, perceived susceptibility, self-efficacy, and regular larval survey behavior were measured for program outputs. Container Index (CI), House Index (HI), and Breteau Index (BI) were used to confirm program outcomes. Key community stakeholders in the experimental village were identified and empowered through active learning in the village. Monthly meetings with the key stakeholders were used to share experiences learned, to reflect on the program outputs and outcomes as well as to plan for the next cycle of program activities. The program was quite successful. Knowledge, perception, self-efficacy, and larval survey practices in the experimental group were significantly higher than before the experiment, and higher than the comparison group. CI, HI, and BI were decreased sharply to better than the national target. Community status as community leaders was the best predictor for larval survey behavior at the first survey. Participating in the study program activities was the best predictor at the end of the program. The results from this study suggest that the dengue hemorrhagic fever (DHF) prevention and control program at the sub-district health level should be more proactive and emphasized at the village level. Monitoring the disease control program outputs and outcomes should be performed regularly during monthly meetings. Finally, local health officers need to be empowered for these matters.

Causal relationship between health promoting behavior and quality of life in cervical cancer patients undergoing radiotherapy.

The purpose of this cross-sectional study was to examine the causal relationships among age, education, family income, and stage of carcinoma, perceived benefits, perceived barriers, perceived self-efficacy, health promoting behavior and quality of life in patients with cervical cancer. Pender's Health Promotion Model (1996) provided a guide for the conceptual framework of this study. Purposive sampling was employed to recruit 488 cervical cancer patients who were undergoing radiotherapy at seven public hospitals in five areas of Thailand. The instruments used in this study included a Personal Data Form, Cognitive perception Form, Health promoting behavior scale, the social support questionnaire and The Functional Assessment of Cancer Therapy General (FACT-G) form. The proposed model was tested and modified by the LISREL Program. The modified model adequately fitted with the data. The results demonstrate that health promoting behavior had a significant direct positive effect on quality of life (beta = 0.71, p < 0.01). Cognitive perceptual factors had a significant direct effect on health promoting behaviors (P = 0.69, p < 0.01). Social support had a significant direct effect on the cognitive perceptual factors (P = 0.64, p < 0.01), health promoting behavior (beta = 0.70, p < 0.01), and the quality of life (beta = 0.48, p < 0.01). Age and education did not have a significant total effect on the quality of life. Family income had a significant direct effect on cognitive perceptual factors (beta = 0.10, p < 0.05). The stage of cancer had a significant direct negative effect on cognitive perceptual factors (beta = -0.11, p < 0.05) and the quality of life (beta = -0.12, p < 0.01). The direct effect of the predictors on the quality of life indicated that cervical cancer patients with higher practice of health promoting behavior tended to have a higher quality of life. The findings indicate that Pender's Health Promotion Model is a useful guide for explaining and predicting the health promoting behavior and the quality of life of Thai cervical cancer patients who were undergoing radiotherapy. The significance of cognitive perceptual factors and social support confirm health promoting behavior as a goal directed towards the level of well being. This has implications for health care systems in planning interventions to promote health promoting behavior in a health promotion setting in cervical cancer patients for a better quality of life and healthy. A longitudinal study and experimental study are recommended for further study.

An ergonomics intervention program to prevent worker injuries in a metal autoparts factory.

An ergonomics intervention program (EIP) was conducted with male employees working in the pressing and storage sections of a metal autoparts factory in Samut Prakan Province, Thailand. The objectives of this study were to assess the causes of injuries in the pressing and storage sections of that factory, and to improve working conditions by reducing worker injuries from accidents and low back muscular discomfort, using an EIR The study design used a participatory research approach which was quasi-experimental with pretest-posttest evaluations, with a non-equivalent control group. A total of 172 male participants working in Building A were the target group for assessing causes of injury. A retrospective study of official accident information, and questionnaires for general information, health and muscular discomfort, injury frequency rate (IFR), injury severity rate (ISR), medical expenses, and EIP design. Two groups of employees volunteered for the study on muscular back discomfort. The first group of 35 persons volunteered to participate in the EIP (EIP group), and the second 17 persons from Building B did not (non-EIP group). The EIP was composed of 4 major categories: (1) engineering improvement, (2) change in personal protective equipment, (3) environmental improvement, (4) administrative intervention, training, and health education. Low back muscular discomfort was measured through questionnaires on subjective feelings of muscular discomfort, and by surface electromyography (sEMG). Muscle activities were measured by sEMG of the left and right erector spinae and multifidus muscles, and evaluated by multivariate test for dependent samples (paired observation), and multivariate test for two independent samples. After EIP, IFR decreased 65.46%, ISR decreased 41.02%, and medical expenses decreased 42.79%. The low back muscular loads of the EIP group were significantly reduced, with a 95% confidence level (p < 0.05) while those of the non-EIP group were not. Subjective feelings of muscular discomfort, determined by Wilcoxon Signed Ranks test, showed that after applying the EIP to the EIP group, the mean scores for general bodily discomfort and low back muscular discomfort in the EIP group had significantly reduced, while those of the non-EIP group increased, (p < 0.05).

The association between environmental factors and tuberculosis infection among household contacts.

A cross-sectional study was conducted to determine the association between environmental factors and tuberculosis infection among household contacts aged less than 15 years in Bangkok, Thailand, between May and December 2003. During the study period, 480 household contacts aged under 15 years were identified. The prevalence of tuberculosis infection among household contacts was 47.08% (95% CI = 42.60-51.56). A generalized estimating equation (GEE) indicated that the risk of positive tuberculin skin testing in household contacst was found to increase with household crowding. Children living in a crowded household were five times more likely to have tuberculosis infection (OR = 5.19, 95% CI = 2.65-8.69). The association between environmental factors and tuberculosis infection assists community tuberculosis staff in understanding the risks for tuberculosis infection in the community and planning appropriate preventive actions based on this risk.

Factors associated with the household contact screening adherence of tuberculosis patients.

A cross-sectional study was conducted to explore factors associated with the adherence of tuberculosis patients in bringing their household contacts to a TB clinic in Bangkok, Thailand. During the study period, May to December 2003, 325 sputum-smear-positive tuberculosis patients were recruited into the study. Of the 325 eligible tuberculosis patients, 169 (52.00%, 95% Cl = 47.00-57.00) brought their household contacts to the TB clinic. Psychosocial and cues to action factors were examined as indicators of the household contact screening adherence of tuberculosis patients. The results reveal that the household contact screening adherence of tuberculosis patients was significantly associated with a higher perceived susceptibility (Adjusted OR = 2.90, 95% Cl = 1.18-7.16), lower perceived barriers (Adjusted OR = 4.60, 95% CI = 1.99-10.60), a higher intention to bring the contacts to the TB clinic (Adjusted OR = 3.35, 95% Cl = 1.44-7.76), and a short distance from home to the TB clinic (Adjusted OR = 11.47, 95% Cl = 4.57-28.79). The results from this study provide information for TB clinic staff for developing an appropriate intervention program. Through effective intervention and active policy enforcement, a higher percentage of household contact screening adherences can be achieved.

Simultaneous determination of trans, transmuconic acid and s-phenylmercapturic acid by high pressure liquid chromatography and its application.

The simultaneous determination of urinary trans,trans-muconic acid (t,t-MA) and S-phenylmercapturic acid (S-PMA) was performed by liquid extraction with ethyl acetate and reversed-phase high performance liquid chromatography (RP-HPLC) on a Hypersil-ODS column using the gradient mobile phase of methanol and 0.0012 N perchloric acid and diode array detection at 205 and 264 nm for S-PMA and t,t-MA, respectively. The retention times for t,t-MA and S-PMA were 3.8 and 12.3 minutes, respectively. The recoveries of t,t-MA and S-PMA were > 97%; between-day precisions were all within 8% RSD (100x SD/mean). The method was applied to analyze the urinary t,t-MA and S-PMA of 59 service station attendants exposed to average benzene concentrations in the air of 0.20+/-0.18 ppm. Significant differences in pre-shift and post-shift urinary t,t-MA between smokers and non-smokers were found.

Health seeking behavior among insured persons under the Social Security Act, 1990.

Since having health insurance cannot guarantee access to care among the insured persons, their actual health seeking behavior should be evidence reflecting true access. Therefore, the study aimed to present the patterns of health seeking behavior among the insured persons who actually were able to get free services from their registered hospitals under the Social Security Scheme. Purposive sampling was done of 1,003 insured persons who were willing to participate in the study from small, medium and large establishments in the Huai Khwang district in Bangkok. A health diary was employed as one of the data collecting tools with a follow-up period of six months. The average illness rate found was 6.44 episodes/person/year. The characteristics of illnesses reported were described in terms of symptom groups, perceived severity, duration, work or non-work related cause. No treatment or self care, seeking help from non-registered health facilities and seeking help from registered hospitals and clinics were the patterns of health seeking behaviors found in the study. The patterns of health seeking behaviors among the participants varied depending on the stage of treatment, perceived severity of illness and types of additional health benefits. Seeking care from registered hospitals and clinics was found among the illnesses with a higher level of perceived severity, among the participants with chronic diseases, and among the illnesses that were treated with higher stages. Therefore, health insurance might not be able to guarantee true access to needed care for people unless the comprehensive health care provider networks are designed to cover more types of services, be more convenient and have more accessible health care providers.

Risk factors for tuberculosis infection among household contacts in Bangkok, Thailand.

A cross-sectional study was conducted to determine the prevalence of tuberculosis infection and risk factors for tuberculosis infection among household contacts aged less than 15 years in Bangkok, Thailand, between August 2002 and September 2003. During the study period, 342 index cases with sputum smear positive pulmonary tuberculosis patients were recruited into the study and their 500 household contacts aged under 15 years were identified. The prevalence of tuberculosis infection among household contacts was found to be 47.80% (95%CI = 43.41-52.19). In multivariate analysis, a generalized estimating equation (GEE) was used to determine the risk factors for tuberculosis infection among household contacts. The results indicated that the risk of tuberculosis infection was significantly associated with close contact (adjusted OR = 3.31, 95%CI = 1.46-7.45), exposure to female index case (adjusted OR = 2.75, 95%CI = 1.25-6.08), exposure to mother with tuberculosis (adjusted OR = 3.82, 95%CI = 1.44-10.14), exposure to father with tuberculosis (adjusted OR = 2.55, 95%CI = 1.19-5.46), exposure to index case with cavitation on chest radiograph (adjusted OR = 4.43, 95%CI = 2.43-8.05), exposure to index case with 3+ sputum smear grade (adjusted OR = 3.85, 95%CI = 1.92-7.70), and living in crowded household (adjusted OR = 2.63, 95%CI = 1.18-5.85). The distribution of tuberculosis infection and risk factors among contact cases are significant for health care staff in strengthening and implementing tuberculosis control programs in Thailand.

Spectrophotometric determination of plasma and red blood cell cholinesterase activity of 53 fruit farm workers pre- and post-exposed chlorpyrifos for one fruit crop.

We sought to investigate the early biological effects of chlorpyrifos among 53 Thai fruit farm workers by measuring the plasma cholinesterase (PChE) and red blood cell cholinesterase (AChE) activities, a biomarker of organophosphate (OPs) pesticide during one fruit crop. The ChE activity (V(m)/K(m)) was spectrophotometrically analyzed before and after exposing to chlorpyrifos. The V(m)/K(m) values of both non-spraying and spraying seasons are found as normal distribution pattern. The median PChE and AChE activities among farm workers in the non-spraying season were 2.3 x 10(-3) s(-1) and 7.26 x 10(-5) s(-1), respectively. The median PChE and AChE activities of the farm workers in the spraying season were 2.02 x 10(-3) s(-1) and 5.95 x 10(-5) s(-1), respectively. The mean V(m)/K(m) values of PChE shifted left (t-test, p=0.013), indicating a decrease in PChE activity in the farm workers exposed to chlorpyrifos. However, the V(m)/K(m) values of AChE in nonspraying season and in the spraying season were not different (t-test, p=0.246). We propose that PChE activity can be used as a biomarker for monitoring early toxicity induced by chlorpyrifos insecticide.