Enzyme-linked immunosorbent assay (ELISA) immunoassaying versus microscopy: advantages and drawbacks for diagnosing giardiasis

Giardia lamblia Immunoassay: Systematic review and meta-analysis

Immunoassays are important tools in diagnosing giardiasis, though there are several controversies inherent in the existing methods. We conducted a systematic review and meta-analysis to assess the pooled diagnostic accuracy of immunoassays in detecting the gastrointestinal disease-causing parasite Giardia lamblia. Our comprehensive search, which included PubMed, Scopus, and ScienceDirect from 2000 up until 2023, resulted in 34 studies reporting the performance of 24 different immunoassays. The overall pooled sensitivity and specificity of immunoassays and subgroup analyses were determined. Notably, ImmunoCardSTAT® and RIDASCREEN® Giardia were the most used assays (n = 6 studies each). They exhibited sensitivity and specificity of 84 % and 99 % and 93 % and 99 %, respectively. Sub-group analysis on the type of immunoassays (without the case-control studies) showed that commercial ELISA had higher sensitivity (96 %) compared to a commercial immunochromatographic (88 %), which justifies the difference of sensitivity between ImmunoCardSTAT® and RIDASCREEN® Giardia. However, the applicability between these two in clinical settings, replacing the gold standard, should be considered including the time, equipment requirement, and budget. Samples from symptomatic patients showed higher sensitivity (92 %) compared to asymptomatic patients (79 %). Overall, immunoassays can be a practical replacement for the current gold standard, but more information should be gathered regarding the cost of providing more conclusive suggestions on these findings.

Microbiological quality of irrigation water for cultivation of fruits and vegetables: An overview of available guidelines, water testing strategies and some factors that influence compliance

Contaminated irrigation water is among many potential vehicles of human pathogens to food plants, constituting significant public health risks especially for the fresh produce category. This review discusses some available guidelines or regulations for microbiological safety of irrigation water, and provides a summary of some common methods used for characterizing microbial contamination. The goal of such exploration is to understand some of the considerations that influence formulation of water testing guidelines, describe priority microbial parameters particularly with respect to food safety risks, and attempt to determine what methods are most suitable for their screening. Furthermore, the review discusses factors that influence the potential for microbiologically polluted irrigation water to pose substantial risks of pathogenic contamination to produce items. Some of these factors include type of water source exploited, irrigation methods, other agro ecosystem features/practices, as well as pathogen traits such as die-off rates. Additionally, the review examines factors such as food safety knowledge, other farmer attitudes or inclinations, level of social exposure and financial circumstances that influence adherence to water testing guidelines and other safe water application practices. A thorough understanding of relevant risk metrics for the application and management of irrigation water is necessary for the development of water testing criteria. To determine sampling and analytical approach for water testing, factors such as agricultural practices (which differ among farms and regionally), as well as environmental factors that modulate how water quality may affect the microbiological safety of produce should be considered. Research and technological advancements that can improve testing approach and the determination of target levels for hazard characterization or description for the many different pollution contexts as well as farmer adherence to testing requirements, are desirable.

COVID-19 diagnostic methods in developing countries

COVID-19 has become one of the few leading causes of death and has evolved into a pandemic that disrupts everyone's routine, and balanced way of life worldwide, and will continue to do so. To bring an end to this pandemic, scientists had put their all effort into discovering the vaccine for SARS-CoV-2 infection. For their dedication, now, we have a handful of COVID-19 vaccines. Worldwide, millions of people are at risk due to the current pandemic of coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2). Despite the lack of clinically authorized antiviral medications and vaccines for COVID-19, clinical trials of many recognized antiviral agents, their combination, and vaccine development in patients with confirmed COVID-19 are still ongoing. This discovery gave us a chance to get immune to this disease worldwide and end the pandemic. However, the unexpected capacity of mutation of the SARS-CoV-2 virus makes it difficult, like the recent SAS-CoV-2 Omicron variant. Therefore, there is a great necessity to spread the vaccination programs and prevent the spread of this dreadful epidemic by identifying and isolating afflicted patients. Furthermore, several COVID-19 tests are thought to be expensive, time-consuming, and require the use of adequately qualified persons to be carried out efficiently. In addition, we also conversed about how the various COVID-19 testing methods can be implemented for the first time in a developing country and their cost-effectiveness, accuracy, human resources requirements, and laboratory facilities.

Rapid on-site diagnosis of canine giardiosis: time versus performance

BACKGROUND

Infections by protozoans of the genus Giardia are a common cause of diarrhea in dogs. Canine giardiosis constitutes a disease with a zoonotic potential; however, it is often underestimated due to its challenging diagnosis. The objective of the study was to assess the diagnostic performance of an immunochromatographic strip test (SpeedTM Giardia, Virbac, France) comparing it with microscopy (zinc sulfate flotation) by utilizing the combination of an enzyme immunoassay (ProSpecTTM Giardia EZ Microplate Assay, Oxoid Ltd., UK) and the PCR as the gold standard. A positive result in both ELISA and PCR was set as the gold standard.

METHODS

Initially, fecal samples from dogs with clinical signs compatible with giardiosis were tested with the SpeedTM Giardia test and separated into two groups of 50 samples each: group A (positive) and group B (negative). Thereafter, all samples were examined by zinc sulfate centrifugal flotation technique and assayed by the ProSpecTTM Giardia Microplate Assay and PCR. The performance of the SpeedTM Giardia and zinc sulfate centrifugal flotation tests were calculated estimating sensitivity, specificity, and positive and negative likelihood ratio; the chi-square and McNemar tests were used for the comparison of the two methods.

RESULTS

Giardia cysts were not detected by microscopy in 16 out of the 50 samples (32%) of group A and in none of group B samples. Eight out of 50 samples in group B (16%) were tested positive both with the ProSpecTTM Giardia Microplate Assay and PCR. Fecal examination with the SpeedTM Giardia test was more sensitive (86.2%) than the parasitological method (58.6%, P < 0.001) while the specificity of both methods was 100%.

CONCLUSIONS

The SpeedTM Giardia test is an easy-to-perform diagnostic method for the detection of Giardia spp., which can increase laboratory efficiency by reducing time and cost and decrease underdiagnosis of Giardia spp. infections. This immunochromatographic strip test may be routinely exploited when a rapid and reliable diagnosis is required, other diagnostic techniques are unavailable and microscopy expertise is inefficient. In negative dogs with compatible clinical signs of giardiosis, it is recommended either to repeat the exam or proceed with further ELISA and PCR testing.

Modification of the Alere GIARDIA Ag TEST immunochromatography KIT methodology for its use in frozen fecal sediment of dogs and cats

Giardia duodenalis is a worldwide intestinal parasite and is one of the most frequent protozoa species infecting dogs and cats. This study aimed to modify the methodology of Alere GIARDIA Ag TEST KIT for its use in frozen fecal sediments with different storage times in a freezer (-20°C), thus expanding the range of use of this methodology. One hundred fecal sediments from dogs (n=50) and cats (n=50) previously examined by optical microscopy for Giardia cysts were selected for this study. The agreement between the modified immunochromatography and microscopy results was calculated by Kappa coefficient. To evaluate the performance of the modified immunochromatography assay on samples with different storage time, the fecal sediments were divided into three groups according to the time of storage in a freezer: (a) ≤ 1 year (n=37); (b) > 1 year and ≤ 3 years (n=39); (c) > 10 years (max. 13 years) (n=24). The results obtained by the modified immunochromatography assay demonstrates a higher sensitivity of this technique when compared with microscopy, regardless of the frozen storage time. These results allow for the use of this methodology in a greater scope of analysis, especially in frozen fecal sediment triage in sample collections, enabling epidemiological and comparative analysis along different decades.

Assessment of the diagnostic performance of four methods for the detection of Giardia duodenalis in fecal samples from human, canine and feline carriers

Enteric parasitic diseases including giardiasis are of public health concern. Different methods are available for the diagnosis of this parasitic infection in fecal samples such as the identification of protozoan cysts and trophozoites by light microscopy, detection of specific antigens by ELISA, and amplification of DNA fragments by PCR. The present study aimed at assessing the performance of four laboratory tests for the detection of Giardia duodenalis in fecal specimens from three different host species with a previous diagnosis of giardiasis; canine, feline and human patients provided new stool samples to be retested for Giardia before initiating treatment with antiprotozoal drugs. For this purpose, triplicate fecal specimens from 54 humans, 24 dogs and 18 cats living in the city of Niterói, RJ, southeast Brazil, were analysed by light microscopy, ELISA, immunochromatography, and nested PCR. The centrifugal-flotation method detected Giardia cysts in 89.6% (86/96) of the fecal samples. The protozoan parasite was detected via immunochromatography in 87.5% (84/96) of these samples. Giardia was detected by ELISA in 69.8% (67/96) of the stool specimens from carriers with a previous diagnosis of Giardia infection. Giardia was detected by PCR in only 39.6% (38/96) of the fecal specimens. Based on these findings, we suggest that, among the four assays that were used in this study, the zinc sulphate flotation technique (Faust et al., 1939) is the best diagnostic assay in terms of sensitivity and specificity to detect G. duodenalis on serially collected samples from dogs, cats and humans.

Protozoa PCR: boon or bane

Parasite detection in faeces has traditionally been performed by microscopy, a procedure that is labour-intensive and highly specialised. In addition, identification by microscopy based on morphological features alone is subjective and prone to wide variability. Although enzyme immunoassays (EIA) of high sensitivity have been developed1 they can detect only a limited range of pathogens. Given these factors the introduction of Polymerase Chain Reaction (PCR) into the routine diagnostic laboratory has improved parasite detection rates2. The ability to multiplex has enabled the detection of multiple targets from a single sample and provides an objective alternative to identification by morphology.

Adaptation of Ritchie's Method for Parasites Diagnosing with Minimization of Chemical Products

Latin America, Africa, and Asia present wide dissemination and high prevalence rates of waterborne parasitic diseases, which is a strong indicative of the fragility of public sanitation systems. In this context, parasitological analyses represent extremely relevant instruments. Several parasite diagnosis methods exist, among which Ritchie's method (1948) stands out. This method uses formaldehyde and ether, two reagents of toxicological importance that can cause damages to environmental and occupational health. The present study aimed to compare Ritchie's method modified by Régis Anécimo, without use of solvents, with the traditional Ritchie's method, routinely used for helminth and protozoa diagnosing in Brazil. Some changes were introduced in the modified method, such as controlled increase of water temperature used after stool dilution and substitution of formaldehyde and ether by a neutral detergent before material centrifugation for observation of parasites. In examined samples by both methods, multiple infections were commonly observed; the modified method presented a similar sensitivity to identify the parasites. The development of analytic diagnosis methods that minimize the use of chemical products like ether and formaldehyde represents an important tool to prevent occupational diseases among exposed professionals, as well as to preserve environmental quality through the use of clean techniques.