Diagnostic accuracy of loop-mediated isothermal amplification in detection of Clostridium difficile in stool samples: a meta-analysis

Laboratory diagnosis of Clostridioides difficile infection in symptomatic patients: what can we do better?

The laboratory diagnosis of Clostridioides difficile infection (CDI) is challenging since this bacteria may be detected in healthy people and toxin production detection is not sensitive enough to be used alone. Thus, there is no single test with adequate sensitivity and specificity to be used in laboratory diagnosis. We evaluated the performance of tests used in the diagnosis of CDI in symptomatic patients with risk factors in hospitals in southern Brazil. Enzyme immunoassays (EIA) for glutamate dehydrogenase antigen (GDH) and toxins A/B, real-time polymerase chain reaction (qPCR), GeneXpert system, and a two-step algorithm comprising GDH/TOXIN EIA performed simultaneously followed by GeneXpert for outliers were evaluated. Toxigenic strain in stool culture was considered CDI positive (gold standard). Among 400 samples tested, 54 (13.5%) were positive for CDI and 346 (86.5%) were negative. The diagnosis of the two-step algorithm and qPCR had an excellent performance with an accuracy of 94.5% and 94.2%, respectively. The Youden index showed that GeneXpert as a single test (83.5%) and the two-step algorithm (82.8%) were the most effective assays. Diagnosing CDI and non-CDI diarrhea could be successfully attained by the combination of clinical data with accuracy of laboratory tests.

Loop mediated isothermal amplification of Clostridioides difficile isolates in gastrointestinal patients

This study investigated the prevalence of Clostridioides difficile by culture, multiplex polymerase chain reaction (M-PCR), and loop mediated isothermal amplification (LAMP) in patients with suspected C. difficile infections (CDIs). Also, the results of three methods were compared. All stool specimens collected from CDI suspected patients were cultured on selective C. difficile cycloserine-cefoxitin fructose agar and incubated in an anaerobic jar up to 7 days. The bacterial isolates were identified using standard tests. Multiplex-PCR (M-PCR) was performed for detection of tcdA, tcdB, and tpi genes. The LAMP assay was performed to detect the tcdB gene of C. difficile. C. difficile was isolated from 20.0% (n = 10/50) of samples by culture. M-PCR showed that 34.0% (n = 17/50) of the specimens were positive for C. difficile based on the presence of tpi gene. Out of the 17 C. difficile, 13 strains (76.0%) were positive for tcdB gene using M-PCR. However, the LAMP assay showed that 30.0% (15/50) of specimens were positive for the presence of tcdB gene. M-PCR and LAMP methods showed 100.0% sensitivity compared to the culture method. However, the specificity of the LAMP (87.5%) was relatively higher than the M-PCR (82.5%) compared to the culture. Based on the results of this study, the prevalence of toxigenic C. difficile strains was high in suspected CDI patients. So, the differentiation between toxigenic and non-toxigenic strains is necessary. Our data showed that the LAMP assay is a good method for direct detection of toxigenic C. difficile strains from stool specimens.

Clostridioides difficile laboratory diagnostic techniques: a comparative approach of rapid and molecular methods

Clostridioides difficile infection is a public health problem because of it is easily spread; with harmful consequences, it is essential to reduce hospital costs and prevent its dissemination by having a precise diagnosis. The gold standard for its diagnosis is polymerase chain reaction (PCR); however, the technique is not available for all laboratories due to the high cost. New approaches using non-molecular tests to detect C. difficile and toxin A/B production has been proposed to improve cost benefits. The objective of this study is to compare molecular methods (PCR) and rapid methods (immunochromatographic test and enzymatic immunoassay). A series of tests comprising these diagnostic techniques was performed with 50 patients with a clinical diagnosis for Clostridioides difficile on GeneXpert® devices test; a calculation of the sensitivity was executed, followed by a comparison of the efficiency of all techniques. Greater sensitivity was observed in the PCR-based methods (BD MAX™ and BioFire FilmArray®) and the GDH-based assays (RIDASCREEN® and Alere Techlab®). The proposed algorithm represents minor monetary disadvantages but a significant temporal optimization of 10%. Future studies concerning both positive and negative results could be advantageous because of the possibility of calculating more method concordance indexes, such as the specificity and Kappa index, in addition to being able to indicate a monetary profit if the proposed algorithm was applied due to the nonproceeding PCR cases.

Interferon-γ release assays for tuberculous meningitis diagnosis: a meta-analysis

INTRODUCTION

Tuberculous meningitis (TBM) is still a great challenge to global public health. As conventional diagnostic methods for TBM are unsatisfactory, interferon-γ release assays (IGRAs) have been introduced for TBM diagnosis tentatively. However, the role of IGRAs for diagnosing TBM remains unclear. Thus, we systematically evaluated the diagnostic performance of cerebrospinal fluid (CSF) and peripheral blood (PB) IGRAs in TBM to fill this blank.

MATERIAL AND METHODS

Relevant studies were systematically searched in both foreign and Chinese databases up to March 2018. Studies in which TBM diagnosis was based on microbiological or clinical criteria were included. The quality of the included studies was assessed through the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. Main outcome measures, including sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR) and diagnostic odds ratio (DOR), were pooled statistically using random effects models. The potential heterogeneity was explored by threshold effect analysis, subgroup analyses and meta-regression. Funnel plots and Egger's test were used to test the potential publication bias. Statistical analyses were performed using Stata and Meta-DiSc software.

RESULTS

Twenty-six out of 656 publications were eligible for meta-analysis, including 1892 participants in total. The pooled estimates of PB IGRAs for TBM diagnosis are as follows: sensitivity: 0.81 (95% CI: 0.78-0.84); specificity: 0.76 (95% CI: 0.73-0.78); PLR: 4.23 (95% CI: 2.95-6.07); NLR: 0.24 (95% CI: 0.19-0.32) and DOR: 21.06 (11.91-37.24). The corresponding estimates for CSF IGRAs were obtained: sensitivity: 0.81 (95% CI: 0.76-0.85); specificity: 0.89 (95% CI: 0.86-0.92); PLR: 7.87 (95% CI: 4.98-12.46); NLR: 0.19 (95% CI: 0.13-0.29); and DOR: 47.74 (25.02-91.12).

CONCLUSIONS

The diagnostic performance of IGRAs is suboptimal. In terms of cost, turn-around time and accessibility, these assays are unsuitable for use as biomarkers for TBM diagnosis.

A systematic review and meta-analysis on the treatment of liver hydatid cyst using meta-MUMS tool: comparing PAIR and laparoscopic procedures

INTRODUCTION

There is an academic debate over surgical treatments of liver hydatid cyst disease. In this study, a systematic review and meta-analysis were carried out in order to evaluate the pros and cons of both PAIR (Puncture, Aspiration, Injection, Respiration) and laparoscopic techniques by considering the outcomes of liver hydatid cysts.

MATERIAL AND METHODS

We designed descriptive Boolean queries to search two databases, PubMed and Scopus, to derive the articles published in the period of January 2000 to December 2016 in order to evaluate the outcomes of these research articles. The outcomes of laparoscopic and PAIR procedures include the rates of cure, postoperative complications, recurrences, and mortality, which were extracted, assessed, and used as their corresponding effect sizes.

RESULTS

Fifty-seven studies including a total of 2832 patients (PAIR group n = 1650 and laparoscopic group = 1182) were analyzed. In this meta-analysis study, a random effect model of correlations of outcomes (postoperative complications, mortalities, recurrences, and cure rates) of PAIR and laparoscopy procedures was used. The meta-analysis and the forest plots of the two procedures show that the PAIR approach is superior in terms of cure, complication, and mortality rates compared with the laparoscopy technique. However, the recurrence rate is low in laparoscopic approaches. Moreover, Egger's tests for determining publication bias and heterogeneity tests were also performed.

CONCLUSIONS

This study shows promising trends toward an advantage of PAIR procedures in treatment of liver hydatid cyst in comparison with laparoscopic procedures. The PAIR procedure is superior to laparoscopy due to having a higher cure rate and lower complication and mortality rates; however, the latter has a lower recurrence rate.

Diagnosis of Clostridium difficile infection using an UPLC-MS based metabolomics method

INTRODUCTION

The fecal metabolome of Clostridium difficile (CD) infection is far from being understood, particularly its non-volatile organic compounds. The drawbacks of current tests used to diagnose CD infection hinder their application.

OBJECTIVE

The aims of this study were to find new characteristic fecal metabolites of CD infection and develop a metabolomics model for the diagnosis of CD infection.

METHODS

Ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) was used to characterize the fecal metabolome of CD positive and negative diarrhea and healthy control stool samples.

RESULTS

Diarrhea and healthy control samples showed distinct clusters in the principal components analysis score plot, and CD positive group and CD negative group demonstrated clearer separation in a partial least squares discriminate analysis model. The relative abundance of sphingosine, chenodeoxycholic acid, phenylalanine, lysophosphatidylcholine (C16:0), and propylene glycol stearate was higher, and the relative abundance of fatty amide, glycochenodeoxycholic acid, tyrosine, linoleyl carnitine, and sphingomyelin was lower in CD positive diarrhea groups, than in the CD negative group. A linear discriminant analysis model based on capsiamide, dihydrosphingosine, and glycochenodeoxycholic acid was further constructed to identify CD infection in diarrhea. The leave-one-out cross-validation accuracy and area under receiver operating characteristic curve for the training set/external validation set were 90.00/78.57%, and 0.900/0.7917 respectively.

CONCLUSIONS

Compared with other hospital-onset diarrhea, CD diarrhea has distinct fecal metabolome characteristics. Our UPLC-MS metabolomics model might be useful tool for diagnosing CD diarrhea.

Stem loop-mediated isothermal amplification test: comparative analysis with classical LAMP and PCR in detection of Entamoeba histolytica in Kenya

BACKGROUND

Entamoeba histolytica, the causative agent for amoebiasis is a considerable burden to population in the developing countries where it accounts for over 50 million infections. The tools for detection of amoebiasis are inadequate and diagnosis relies on microscopy which means a significant percent of cases remain undiagnosed. Moreover, tests formats that can be rapidly applied in rural endemic areas are not available.

METHODS

In this study, a loop-mediated isothermal test (LAMP) based on 18S small subunit ribosomal RNA gene was designed with extra reaction accelerating primers (stem primers) and compared with the published LAMP and PCR tests in detection of E. histolytica DNA in clinical samples.

RESULTS

The stem LAMP test indicated shorter time to results by an average 11 min and analytical sensitivity of 10^-7 (~30 pg/ml) compared to the standard LAMP and PCR which showed sensitivities levels of 10^-5 (~3 ng/ml) and 10^-4 (~30 ng/ml) respectively using tenfold serial dilution of DNA. In the analysis of clinical specimens positive for Entamoeba spp. trophozoites and cysts using microscopy, the stem LAMP test detected E. histolytica DNA in 36/126, standard LAMP test 20/126 and PCR 17/126 cases respectively. There was 100% agreement in detection of the stem LAMP test product using fluorescence of SYTO-9 dye in real time machine, through addition of 1/10 dilution of SYBR^® Green I and electrophoresis in 2% agarose gel stained with ethidium bromide.

CONCLUSION

The stem LAMP test developed in this study indicates potential towards detection of E. histolytica.

Diagnostic test accuracy of glutamate dehydrogenase for Clostridium difficile: Systematic review and meta-analysis

We performed this systematic review and meta-analysis to assess the diagnostic accuracy of detecting glutamate dehydrogenase (GDH) for Clostridium difficile infection (CDI) based on the hierarchical model. Two investigators electrically searched four databases. Reference tests were stool cell cytotoxicity neutralization assay (CCNA) and stool toxigenic culture (TC). To assess the overall accuracy, we calculated the diagnostic odds ratio (DOR) using a DerSimonian-Laird random-model and area the under hierarchical summary receiver operating characteristics (AUC) using Holling’s proportional hazard models. The summary estimate of the sensitivity and the specificity were obtained using the bivariate model. According to 42 reports consisting of 3055 reference positive comparisons, and 26188 reference negative comparisons, the DOR was 115 (95%CI: 77–172, I² = 12.0%) and the AUC was 0.970 (95%CI: 0.958–0.982). The summary estimate of sensitivity and specificity were 0.911 (95%CI: 0.871–0.940) and 0.912 (95%CI: 0.892–0.928). The positive and negative likelihood ratios were 10.4 (95%CI 8.4–12.7) and 0.098 (95%CI 0.066–0.142), respectively. Detecting GDH for the diagnosis of CDI had both high sensitivity and specificity. Considering its low cost and prevalence, it is appropriate for a screening test for CDI.