Guidelines for the microbiological quality of treated wastewater used in agriculture: recommendations for revising WHO guidelines

Three different approaches for establishing guidelines for the microbiological quality of treated wastewater that is reused for agriculture are reviewed. These approaches have different objectives as their outcomes: the absence of faecal indicator organisms in the wastewater, the absence of a measurable excess of cases of enteric disease in the exposed population and a model-generated estimated risk below a defined acceptable risk. If the second approach (using empirical epidemiological studies supplemented by microbiological studies of the transmission of pathogens) is used in conjunction with the third approach (using a model-based quantitative risk assessment for selected pathogens) a powerful tool is produced that aids the development of regulations. This combined approach is more cost-effective than the first approach and adequately protects public health. The guideline limit for faecal coliform bacteria in unrestricted irrigation (< or = 1000 faecal coliform bacteria/ 100 ml) is valid, but for restricted irrigation < or = 10(5) faecal coliform bacteria/100 ml is recommended when adult farmworkers are exposed to spray irrigation. A limit of < or = 10(3) faecal coliform bacteria/100 ml is recommended if flood irrigation is used or children are exposed. The guideline limit for nematode eggs for both types of irrigation is adequate except when conditions favour the survival of nematode eggs and where children are exposed; in these cases it should be reduced from < or = 1 egg/l to < or = 0.1 egg/l.     

A simplified index of physical health for use in epidemiological studies.

A battery of simple questions designed to measure physical health, in terms of ability to perform physical activities, was appraised in 1839 men and women aged greater than or equal to 50 years in a community survey in Jerusalem. The number of "Yes" answers to six questions, five of which could be skipped if the first one was answered positively, was found to be a satisfactory index, with a high degree of consistency-reliability in the total sample (Cronbach's alpha coefficient = 0.97) and in subgroups categorized by sex, age, education, or father's region of birth. The index constituted an excellent Guttman scale (coefficient of reproducibility = 0.96, coefficient of scalability = 0.94), indicating that the score serves both as a measure of physical health and as an indication of the profile of capabilities. Associations with age and other variables conformed with expectations, attesting the construct validity of the index.     

Development and use of reporting guidelines for assessing the quality of validation studies of health administrative data

Background and Objectives

Validation of health administrative data for identifying patients with different health states (diseases and conditions) is a research priority, but no guidelines exist for ensuring quality. We created reporting guidelines for studies validating administrative data identification algorithms and used them to assess the quality of reporting of validation studies in the literature.

Methods

Using Standards for Reporting of Diagnostic accuracy (STARD) criteria as a guide, we created a 40-item checklist of items with which identification accuracy studies should be reported. A systematic review identified studies that validated identification algorithms using administrative data. We used the checklist to assess the quality of reporting.

Results

In 271 included articles, goals and data sources were well reported but few reported four or more statistical estimates of accuracy (36.9%). In 65.9% of studies reporting positive predictive value (PPV)/negative predictive value (NPV), the prevalence of disease in the validation cohort was higher than in the administrative data, potentially falsely elevating predictive values. Subgroup accuracy (53.1%) and 95% confidence intervals for accuracy measures (35.8%) were also underreported.

Conclusions

The quality of studies validating health states in the administrative data varies, with significant deficits in reporting of markers of diagnostic accuracy, including the appropriate estimation of PPV and NPV. These omissions could lead to misclassification bias and incorrect estimation of incidence and health services utilization rates. Use of a reporting checklist, such as the one created for this study by modifying the STARD criteria, could improve the quality of reporting of validation studies, allowing for accurate application of algorithms, and interpretation of research using health administrative data.     

IgG4 responses to antigens of adult Necator americanus: potential for use in large-scale epidemiological studies.

Described is an epidemiological investigation of hookworm infections in a rural community in Zimbabwe, where Necator americanus is the only human helminth species present. Among a cohort of 120 individuals the overall prevalence of infection was 78%. Intensity of infection was quantified both as egg counts (range: 0-2563 eggs per g of stool) and worm burden (range: 0-100 worms). Although both these measures provide useful quantitative data, they are tedious to determine in large-scale epidemiological studies and may present social and logistic difficulties. As an alternative screening method, we therefore investigated isotype-specific responses to adult worm antigens of N. americanus. The results show that specific IgG4 responses correlate positively and significantly with both measures of intensity and may be a useful marker of hookworm infection.     

A comparison of several methods to test for the existence of a monotonic dose-response relationship in clinical and epidemiological studies.

The Mantel-extension chi-square test for overall trend and an asymptotically equivalent test based on logistic regression are commonly used to test for a monotonic dose-response relationship between exposure and disease in epidemiological and clinical studies. However, these tests present two important disadvantages, as they (i) make the restrictive assumption of a parametric model of linear form on the logit scale and (ii) impose the a priori choice of scores to code for the exposure categories. Indeed, the linear assumption, if made incorrectly, can lead to an invalid conclusion, and the choice of scores lends arbitrariness to the test results. Some alternative tests have been proposed in the literature. We have considered several of these tests, namely one based on isotonic regression, the T-test based on contrasts and a recently published test based on adjacent contrasts (Dosemeci-Benichou test). The aim of our study was to compare the statistical properties (type I error and power) of these tests and of the commonly used Mantel-extension test for overall trend. We generated cohort and case-control data and considered one- and two-sided versions of the tests. Moreover, we studied the tests under the null hypothesis of no relationship between exposure and disease and under various alternative patterns of monotonic or non-monotonic dose-response relationships. This study confirms that the commonly used trend tests can lead to erroneous conclusion of a monotonic dose-response relationship. The test based on isotonic regression does not represent a favourable alternative, as it tends to be too powerful in case of non-monotonic dose-response relationship patterns. The tests based on contrasts seem to possess more favourable properties by combining close to nominal type I error, high power for monotonic alternatives and low power for non-monotonic alternatives.     

Careful use of pseudo R-squared measures in epidemiological studies

Many epidemiological research problems deal with large numbers of exposed subjects of whom only a small number actually suffers the adverse event of interest. Such rare events data can be analysed by employing an approximate Poisson model. The objective of this study is to challenge the interpretability of the corresponding Poisson pseudo R-squared measure. It will lack sensible interpretation whenever the approximate Poisson outcome is generated by counting the number of events within covariate patterns formed by cross-tabulating categorical covariates. The failure is caused by the immanent arbitrariness in the definition of the covariate patterns, that is, independent Bernoulli events, B(1,pi), are arbitrarily combined into binomially distributed ones, B(n,pi), which are then approximated by the Poisson model.     

Risks associated with the microbiological quality of bodies of fresh and marine water used for recreational purposes: summary estimates based on published epidemiological studies

The current European standards for microbiological quality of bathing water (i.e., all running or still fresh waters or parts thereof and/or sea water [with the exception of water intended for therapeutic purposes and water used in swimming pools]) were issued in 1976 and are currently undergoing revision. In this article, the authors propose parameters for select microorganism indicators to assist in the establishment of public-health-based objectives for fresh and marine water quality. A type-II meta-analysis of the results of 18 published epidemiological studies was implemented in an attempt to characterize the relationship(s) between concentrations of bacterial indicators and rates of acute gastrointestinal diseases among bathers who had used fresh or marine water for recreational purposes. The authors fit multiple linear-regression models, which allowed for random effects across studies, to derive dose-response curves. Several confounders and effect modifiers were controlled for in the analyses. Risks were then estimated for a hypothetical individual who would bathe 20 times/yr in water that contained a given concentration of microorganisms. For fresh-water-associated highly credible gastrointestinal illnesses, a level of 10 fecal coliforms/100 ml water yielded an attributable risk of 0.2 cases/1,000 person-years; a risk of 2 cases/1,000 person-years was found for fecal streptococci. The corresponding yearly attributable risks were 1 and 13 cases/1,000 person-years, respectively, for 100 bacteria/100 ml fresh water. Risks associated with fecal coliforms were found to be lower in marine water than in fresh water. Irrespective of the type of water examined, total coliforms were related only weakly with acute digestive morbidity. Developers of future bathing-water standards should state the level of risk deemed acceptable for public health. The authors of this study maintain that levels of fecal coliforms and fecal streptococci should be used as criteria for infectious risk management associated with bodies of marine and fresh water used for recreational purposes.     

Assessing guidelines for use in family practice.

With more than 1000 new guidelines produced annually over the past decade, it is impossible for the practicing family physician to determine which ones should be adapted into their clinical practice. The Ontario Ministry of Health and Long-Term Care and the Ontario Medical Association formed the Guideline Advisory Committee (GAC) in 1997 to assess and disseminate guidelines that would improve the quality and utilization of health care services in the province. Over the past 3 years the GAC has developed a strategy to identify important topics, to rank order guidelines published on these topics based on the quality of their development, and to reformat guidelines as necessary to make them user-friendly for implementation in clinical practice. The GAC is currently assessing a number of strategies to enhance the dissemination of selected guidelines to improve the quality of care delivered in the province.     

Recent advances in molecular diagnostic techniques for human lymphatic filariasis and their use in epidemiological research

Diagnosis of lymphatic filariasis for epidemiological studies is an area of science that has been greatly modernized over the last two decades. Recent developments and the introduction of new technologies have led to the replacement of traditional diagnostic methods that were insensitive, tedious and often impractical with molecular biology techniques that have considerable potential for field use. This paper reviews some of these major new techniques and the applications of molecular diagnosis in the field of lymphatic filariasis.     

Standardizing questionnaire items for the assessment of waterpipe tobacco use in epidemiological studies

Lessons from surveillance of the smoking epidemic show that the lack of adequate attention to standardizing measures and instruments for epidemiological studies has negatively influenced our ability to assess spatial and secular trends in smoking worldwide. Waterpipe smoking, another hazardous form of tobacco use, is gaining popularity worldwide, with societies in the Eastern Mediterranean region (EMR) being most affected. Several research groups are currently investigating the epidemiology of waterpipe smoking among various populations in the EMR. Initial evidence shows that in contrast to usage patterns observed in adult cigarette smoking, waterpipe smoking is characterized mainly by intermittent and social use. As such, many measures that have been traditionally used for the study of usage patterns and dependence among adult cigarette smokers are uninformative for waterpipe smoking. Thus, the need to develop standardized measures and terminology for assessment of the epidemiology of waterpipe smoking in different populations is of paramount importance. As the monitoring of waterpipe smoking is in its infancy, the development of consensus measures should facilitate the initiation of effective surveillance that can guide public health response to this emerging epidemic.     

Measurement precision of an olfactory perception threshold test for use in field studies.

Changes in olfactory function have been associated with workplace exposure to a variety of substances. In the workplace, smell can be particularly important, since it is commonly used to detect potentially hazardous situations or as an indicator of mask cartridge breakthrough. Sensitive quantitative measures of olfactory loss would be useful in epidemiological studies and workplace surveillance. The objective of the present study was to determine the reproducibility of an olfactory perception threshold test and variations with age, gender, and smoking status. The test was a standard olfactory kit (Olfactolab No. 11), including 18 serial dilutions of PM-carbinol, with an equal number of blanks. The forced choice method was used, with both tester and subject blinded as to which bottle contained the odorant. Olfactory perception threshold was recorded when the subject identified the same dilution three times. To assess reproducibility, testing was repeated four times over a period of 4 weeks, on the same weekday and the same time of day. Subjects (n = 63) ranged in age from 20 to 60 years (mean age: 39.7 +/- 12.5 years), 47.6% were women, 29.5% currently smoked, and 27.9% were former smokers. Results showed no inter-week differences in olfactory perception threshold (Analysis of variance for repeated measures: F = 0.59; p much greater than 0.05). Inter-class correlation for assessment of agreement of continuous variables was 0.76. Inter-week concordance of hyposmia showed fair to good agreement (0.55 greater than or equal to kappa less than or equal to 0.66). Three-way analysis of variance (ANOVA) revealed significant differences with respect to age category (F = 7.36; p less than 0.001) and current smoking status (F = 4.54; p less than 0.05), but not for gender (F = 2.32; p greater than 0.05). The multiple regression model with age and smoking as independent variables was highly significant (F = 13.03; p less than 0.001), explaining 28% of the variance; olfactory threshold increased 0.47 ds/year (t = 4.01; p less than 0.001) and 0.27 ds/cigarettes/day (t = 2.46; p less than 0.05). The findings of this study indicate that this test is reproducible and sensitive to expected changes with age and smoking status. It corresponds well to criteria for testing in the field and should be considered for studies characterizing olfactory functions and sensory loss among working populations.     

Comparability of nutrient estimation by three food frequency questionnaires for use in epidemiological studies

Replication of results is an important issue in studies of diet and disease, possibly dependent on data collection method. We compared assessments from the Health Habits and History Questionnaire (HHHQ), the Harvard Semiquantitative Food Frequency Questionnaire (HFFQ), and the New York State Cohort Food Frequency Questionnaire (CFFQ) for estimates of daily intakes of energy, protein, carbohydrates, total fat, dietary fiber, cholesterol, vitamins A, C, and E, and carotenoids. Fifty-nine men and 50 women aged 35-73 years completed the HHHQ and HFFQ as interviews and the 44-food CFFQ as a self-administered mailed questionnaire. Comparability was assessed with Spearman correlation coefficients. Quantitation of nutrient intake differed by nutrient, questionnaire, and nutrient calculation method. Ranking on energy and macronutrient intake for the HHHQ and HFFQ ranged from 0.62 to 0.80; ranking for micronutrient intake ranged from 0.56 to 0.80. For the CFFQ with the HHHQ or HFFQ, correlations ranged between 0.29 and 0.62. The CFFQ performs comparably to the HHHQ and HFFQ for some, but not all, nutrients; our results suggest that the HHHQ and HFFQ can be used interchangeably with reasonable confidence in studies of diet and disease.     

Implementation of the WHO guidelines for the safe use of wastewater in Pakistan: balancing risks and benefits

The use of wastewater in agriculture is receiving renewed attention as a result of increasing global water scarcity. Wastewater use potentially poses a risk to public health if not properly managed. In Pakistan the use of wastewater in agriculture is already common, though in most cases its use is unregulated and wastewater untreated. In a four year study in Faisalabad, Pakistan, the risks and benefits of the use of untreated wastewater in agriculture were assessed. The study found an increased risk of intestinal disease in wastewater farmers but also found major financial and nutritional benefits for farmers and consumers in the city of Faisalabad. This paper presents a policy approach for the implementation of the WHO guidelines for the safe use of wastewater in agriculture in Pakistan.