Nonutility of routine testing of stool for ova and parasites in a tertiary care Canadian centre

Things We Do for No Reason™: Ova and Parasite Testing in Patients With Acute Diarrhea Arising During Hospitalization

Inspired by the ABIM Foundation’s Choosing Wisely® campaign, the “Things We Do for No Reason™” (TWDFNR) series reviews practices that have become common parts of hospital care but may provide little value to our patients. Practices reviewed in the TWDFNR series do not represent clear-cut conclusions or clinical practice standards but are meant as a starting place for research and active discussions among hospitalists and patients. We invite you to be part of that discussion.

An audit of inpatient stool ova and parasite (O&P) testing in a multi-hospital health system

Background & Objectives

Stool ova and parasite (O&P) examinations are routinely ordered initial tests in patients admitted to the hospital with acute diarrhea, despite low test positivity rates. We examined the diagnostic yield of inpatient stool O&P exams and identified risk factors associated with positive tests.

Methods

A retrospective, case-control analysis of inpatients admitted with diarrhea, who underwent O&P examination, was conducted. Clinical and demographic variables of cases were compared with age-and gender-matched controls via uni- and multivariate conditional logistic regression analyses.

Results

The yield of inpatient O&P exams was 2.15% (37/1723). Blastocystisspp. represented the most common parasites. All patients with positive tests, excluding Blastocystisspp., had at least one of the following risk factors: smoking, prior parasitic disease, HIV-positive status, travel to an endemic area, and institutionalization.

Conclusions

Superfluous inpatient stool O&P exams confer a financial and labor burden to hospital systems. Stool O&P exams should be restricted to individuals admitted to the hospital for <3 days, having diarrhea >7 days and possessing at least one of the following risk factors: smoking, prior parasitic disease, HIV-positive status, travel to an endemic area, and institutionalization. Such selective testing can confer a 51% reduction in testing, costs, and labor.

Impact of intestinal parasites on microbiota and cobalamin gene sequences: a pilot study

Background

Approximately 30% of children worldwide are infected with gastrointestinal parasites. Depending on the species, parasites can disrupt intestinal bacterial microbiota affecting essential vitamin biosynthesis.

Methods

Stool samples were collected from 37 asymptomatic children from a previous cross-sectional Argentinian study. A multi-parallel real-time quantitative PCR was implemented for Ascaris lumbricoides, Ancylostoma duodenale, Necator americanus, Strongyloides stercoralis, Trichuris trichiura, Cryptosporidium spp., Entamoeba histolytica and Giardia duodenalis. In addition, whole-genome sequencing analysis was conducted for bacterial microbiota on all samples and analyzed using Livermore Metagenomic Analysis Toolkit and DIAMOND software. Separate analyses were carried out for uninfected, Giardia-only, Giardia + helminth co-infections, and helminth-only groups.

Results

For Giardia-only infected children compared to uninfected children, DNA sequencing data showed a decrease in microbiota biodiversity that correlated with increasing Giardia burden and was statistically significant using Shannonʼs alpha diversity (Giardia-only > 1 fg/µl 2.346; non-infected group 3.253, P = 0.0317). An increase in diversity was observed for helminth-only infections with a decrease in diversity for Giardia + helminth co-infections (P = 0.00178). In Giardia-only infections, microbiome taxonomy changed from Firmicutes towards increasing proportions of Prevotella, with the degree of change related to the intensity of infection compared to uninfected (P = 0.0317). The abundance of Prevotella bacteria was decreased in the helminths-only group but increased for Giardia + helminth co-infections (P = 0.0262). Metagenomic analysis determined cobalamin synthesis was decreased in the Giardia > 1 fg/µl group compared to both the Giardia < 1 fg/µl and the uninfected group (P = 0.0369). Giardia + helminth group also had a decrease in cobalamin CbiM genes from helminth-only infections (P = 0.000754).

Conclusion

The study results may provide evidence for an effect of parasitic infections enabling the permissive growth of anaerobic bacteria such as Prevotella, suggesting an altered capacity of vitamin B12 (cobalamin) biosynthesis and potential impact on growth and development in children .

AGA Technical Review on the Evaluation of Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome in Adults (IBS-D)

BACKGROUND & AIMS

The evaluation of patients with chronic watery diarrhea represents a diagnostic challenge for clinicians because organic causes, including inflammatory bowel disease, microscopic colitis, and chronic infection, must be differentiated from functional diarrhea and diarrhea-predominant irritable bowel syndrome. The purpose of this review is to summarize the available evidence on the usefulness of diagnostic tests in such patients.

METHODS

We searched MEDLINE and EMBASE via OVID, from 1978 until April 2017. We included diagnostic test accuracy studies reporting on the use of fecal and blood tests for the evaluation of adult patients with functional diarrhea, including irritable bowel syndrome. We assessed the risk of bias of included studies using a modified version of the Quality Assessment of Diagnostic Accuracy Studies II, and the certainty in the evidence using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach. We calculated pooled sensitivity and specificity, and the proportion of patients with true and false positive and negative results. We evaluated the following tests: erythrocyte sedimentation rate, C-reactive protein, fecal lactoferrin, fecal calprotectin, serologic tests for celiac disease, tests for bile acid diarrhea, the commercially available version of anti-cytolethal distending toxin B and anti-vinculin antibodies, and tests for Giardia infection. We did not evaluate breath tests for small intestinal bacterial overgrowth, as they are not part of a standard diarrhea workup.

RESULTS

Thirty-eight studies proved eligible to evaluate 1 or more of these tests. Erythrocyte sedimentation rate and C-reactive protein were similar at discriminating organic from functional disease, with sensitivity and specificity, respectively, of 0.54-0.78 and 0.46-0.95 for erythrocyte sedimentation rate and 0.73 and 0.78 for C-reactive protein. Among fecal tests, fecal calprotectin in a range of 50-60 μg/g (pooled sensitivity 0.81; 95% confidence interval [CI], 0.75-0.86; pooled specificity 0.87; 95% CI, 0.78-0.92) and fecal lactoferrin in a range of 4.0-7.25 μg/g (pooled sensitivity 0.79; 95% CI, 0.73-0.84; pooled specificity 0.93; 95%CI 0.63-0.99) presented the lowest proportion of false-negative results (low certainty in the evidence). Among tests for celiac disease, IgA tissue transglutaminase presented the best diagnostic test accuracy (sensitivity range, 0.79-0.99; specificity range, 0.90-0.99) with moderate certainty in the evidence. Among tests for bile acid diarrhea, the ⁷⁵selenium homotaurocholic acid test performed better than serum fibroblast growth factor 19 and 7α-hydroxy-4-cholesten-3-one, but is not available in the United States. There was insufficient evidence to recommend serologic tests for irritable bowel syndrome at this time. There are several good diagnostic tests for Giardia infection.

CONCLUSIONS

Moderate to low certainty in the evidence indicates that available fecal and blood tests may play a role in the diagnostic workup of adult patients with functional diarrhea. At the moment, no tests are available to reliably rule in irritable bowel syndrome.

Human Intestinal Parasite Burden and Poor Sanitation in Rural Alabama

Hookworm infection affects 430 million people worldwide, causing iron deficiency, impaired cognitive development, and stunting in children. Because of the environmental conditions needed for the hookworm life-cycle, this parasite is endemic to resource-limited countries. Necator americanus was endemic in the southern United States before improvement of sewage disposal systems and eradication programs. With continued poverty, poor sanitation, and an environment suitable for the hookworm life-cycle in some regions of the southern United States, a current prevalence study using modern molecular diagnostics is warranted. Lowndes County, Alabama, was chosen as the study site given previous high hookworm burdens, degree of poverty, and use of open-sewage systems. Participants were interviewed, and stool, serum, and soil samples were tested for nine intestinal parasites using a multiparallel quantitative real-time PCR (qPCR) and enzyme-linked immunosorbent assays. We found that, among 24 households, 42.4% reported exposure to raw sewage within their home, and from 55 stool samples, 19 (34.5%) tested positive for N. americanus, four (7.3%) for Strongyloides stercoralis, and one (1.8%) for Entamoeba histolytica. Stool tested positive for N. americanus contained low levels of parasite DNA (geometric mean 0.0302 fg/μL). Soil studies detected one (2.9%) Cryptosporidium species, and Toxocara serology assay detected one (5.2%) positive in this population. Individuals living in this high-risk environment within the United States continue to have stool samples positive for N. americanus. Gastrointestinal parasites known to be endemic to developing countries are identifiable in American poverty regions, and areas with lower disease burden are more likely to be identified by using qPCR.

The influence of serial fecal sampling on the diagnosis of giardiasis in humans, dogs, and cats

Giardia infection is a common clinical problem in humans and pets. The diagnosis of giardiasis is challenging as hosts intermittently excrete protozoan cysts in their feces. In the present study, we comparatively evaluated two methods of serial fecal sampling in humans, dogs, and cats from Rio de Janeiro, Brazil. The Faust et al. technique was used to examine fecal specimens collected in triplicate from 133 patients (52 humans, 60 dogs, and 21 cats). Specimens from 74 patients were received from the group assigned to carry out sampling on consecutive days - 34 humans, 35 dogs, and 5 cats, and specimens from 59 patients were received from the group assigned to carry out sampling on non-consecutive, separate days - 18 human beings, 25 dogs, and 16 cats. G. duodenalis cysts were found in stools of 30 individuals. Multiple stool sampling resulted in an increase in the number of samples that were positive for Giardia in both groups. The authors therefore conclude that multiple stool sampling increases the sensitivity of the Faust et al . technique to detect G. duodenalis cysts in samples from humans, cats and dogs.

The Global State of Helminth Control and Elimination in Children

Helminth infections, including soil-transmitted helminths and schistosomiasis, remain one of the most common infections in the world with over 1 billion people infected. These infections cause significant morbidity, particularly in young children, that may last a lifetime, including growth and cognitive stunting. There is an urgent need for the control and elimination of helminth infections from areas of poverty to reduce morbidity in children. Mass drug administration programs were adopted by the World Health Assembly in 2001 and have evolved to provide coverage with multiple anthelmintic medications in a single rapid impact package and more extensive coverage within a community.

Molecular testing for clinical diagnosis and epidemiological investigations of intestinal parasitic infections

Over the past few decades, nucleic acid-based methods have been developed for the diagnosis of intestinal parasitic infections. Advantages of nucleic acid-based methods are numerous; typically, these include increased sensitivity and specificity and simpler standardization of diagnostic procedures. DNA samples can also be stored and used for genetic characterization and molecular typing, providing a valuable tool for surveys and surveillance studies. A variety of technologies have been applied, and some specific and general pitfalls and limitations have been identified. This review provides an overview of the multitude of methods that have been reported for the detection of intestinal parasites and offers some guidance in applying these methods in the clinical laboratory and in epidemiological studies.

Diagnostic Algorithm for the Diagnosis of Pediatric Parasitic Gastroenteritis

BACKGROUND

Current practices for ordering stool studies in patients with abdominal and gastrointestinal symptoms are not standardized. We hypothesized that an algorithm involving first-line use of a Cryptosporidium/Giardia combination antigen test and stricter use of ova and parasite (O&P) examinations would be clinically and cost effective.

METHODS

In this study, stool O&P test results for pediatric patients in Dallas, Texas, were reviewed. All results obtained between 2009 and 2012 were included. Patient charts were reviewed to determine test results, symptoms, treatment, travel, and past medical history. Using these data, a retrospective modeling study was done to evaluate the utility of a diagnostic algorithm that limits O&P testing to those patients who are immunocompromised or have travelled outside the United States.

RESULTS

Over the 3-year period of this study, we found that the prevalence of gastrointestinal parasitic disease in children was 1.9%. Analysis of the diagnostic algorithm for the judicious use of stool O&P showed that as much as 65% of testing may be unnecessary and could be eliminated.

CONCLUSIONS

Our findings show that the prevalence of pediatric gastrointestinal parasitic disease in Texas may be lower than expected. In addition, these data show that a diagnostic algorithm limiting O&P testing may be both clinically and cost effective in low-prevalence settings. However, such an algorithm would miss a significant number of infections due to Dientamoeba fragilis and Blastocystis hominis.

Differences in prevalence of parasites in stool samples between three distinct ethnic pediatric populations in southern Israel, 2007-2011

Intestinal parasites cause significant morbidity worldwide, particularly in developing populations. At least three pediatric populations reside in southern Israel: the Bedouin population, the general Jewish population and Jewish children of Ethiopian origin. Our aim was to compare intestinal parasite prevalence between the three pediatric populations in southern Israel. This is a retrospective, laboratory, population-based surveillance. Most ova and parasite (O&P) tests in southern Israel (hospital and community obtained) are performed by the hospital parasitology laboratory. All pediatric stool O&P tests examined by the hospital laboratory between 2007 and 2011 were included. Overall, 45,978 samples were examined; 27,354, 16,969 and 1655 from Bedouin, non-Ethiopian Jewish and Ethiopian children, respectively. 16,317 parasites were identified in 12,325 (26.8%) positive samples. Total prevalences were 36%, 11% and 46% for Bedouin, non-Ethiopian Jewish and Ethiopian children, respectively. Blastocystis hominis, Giardia lamblia and Entamoeba species were the most common parasites identified, constituting ≥80% of positive samples in all groups. Hymenolepis nana was rarely identified in non-Ethiopian Jewish children (0.04% of isolates compared with 2.6% and 0.5% in Bedouin and Ethiopian children, respectively). Other helminths, excluding H. nana and Enterobius vermicularis, were identified almost exclusively in Ethiopian children ≥5years of age. In conclusion, the Bedouin and Ethiopian children were characterized by higher parasite prevalence in stool, compared with the non-Ethiopian Jewish children, probably reflecting higher intestinal parasitic disease rates. Certain helminthic infections were identified almost exclusively in the Ethiopian children. These differences may be associated with lifestyle differences between the three populations.