Sensitivity and specificity of parallel or serial serological testing for detection of canine Leishmania infection

In Brazil, human and canine visceral leishmaniasis (CVL) caused by Leishmania infantum has undergone urbanisation since 1980, constituting a public health problem, and serological tests are tools of choice for identifying infected dogs. Until recently, the Brazilian zoonoses control program recommended enzyme-linked immunosorbent assays (ELISA) and indirect immunofluorescence assays (IFA) as the screening and confirmatory methods, respectively, for the detection of canine infection. The purpose of this study was to estimate the accuracy of ELISA and IFA in parallel or serial combinations. The reference standard comprised the results of direct visualisation of parasites in histological sections, immunohistochemical test, or isolation of the parasite in culture. Samples from 98 cases and 1,327 noncases were included. Individually, both tests presented sensitivity of 91.8% and 90.8%, and specificity of 83.4 and 53.4%, for the ELISA and IFA, respectively. When tests were used in parallel combination, sensitivity attained 99.2%, while specificity dropped to 44.8%. When used in serial combination (ELISA followed by IFA), decreased sensitivity (83.3%) and increased specificity (92.5%) were observed. Serial testing approach improved specificity with moderate loss in sensitivity. This strategy could partially fulfill the needs of public health and dog owners for a more accurate diagnosis of CVL.

Comparative assessment of seller’s staining test (SST) and direct fluorescent antibody test for rapid and accurate laboratory diagnosis of rabies.

Background: Rabies causes 55, 000 annual human deaths globally and about 10,000 people are exposed annually in Nigeria. Diagnosis of animal rabies in most African countries has been by direct microscopic examination. In Nigeria, the Seller’s stain test (SST) was employed until 2009. Before then, both SST and dFAT were used concurrently until the dFAT became the only standard method. Objective: This study was designed to assess the sensitivity and specificity of the SST in relation to the ‘gold standard’ dFAT in diagnosis of rabies in Nigeria. Methods: A total of 88 animal specimens submitted to the Rabies National Reference Laboratory, Nigeria were routinely tested for rabies by SST and dFAT. Results: Overall, 65.9% of the specimens were positive for rabies by SST, while 81.8% were positive by dFAT. The sensitivity of SST in relation to the gold standard dFAT was 81.0% (95% CIs; 69.7% - 88.6%), while the specificity was 100% (95% CIs; 76% - 100%). Conclusion: The relatively low sensitivity of the SST observed in this study calls for its replacement with the dFAT for accurate diagnosis of rabies and timely decisions on administration of PEP to prevent untimely deaths of exposed humans.

Diagnostic value of diffusion weighted MRI and ADC in differential diagnosis of cavernous hemangioma of the liver.

Aims: To investigate the use of diffusion weighted magnetic resonance imaging (DWI) and the apparent diffusion coefficient (ADC) values in the diagnosis of hemangioma. Materials and methods: The study population consisted of 72 patients with liver masses larger than 1 cm (72 focal lesions). DWI examination with a b value of 600 s/mm2 was carried out for all patients. After DWI examination, an ADC map was created and ADC values were measured for 72 liver masses and normal liver tissue (control group). The average ADC values of normal liver tissue and focal liver lesions, the “cut-off” ADC values, and the diagnostic sensitivity and specificity of the ADC map in diagnosing hemangioma, benign and malignant lesions were researched. Results: Of the 72 liver masses, 51 were benign and 21 were malignant. Benign lesions comprised 38 hemangiomas and 13 simple cysts. Malignant lesions comprised 9 hepatocellular carcinomas, and 12 metastases. The highest ADC values were measured for cysts (3.782±0.53×10-3 mm2/s) and hemangiomas (2.705±0.63×10-3 mm2/s). The average ADC value of hemangiomas was significantly higher than malignant lesions and the normal control group (p<0.001). The average ADC value of cysts were significantly higher when compared to hemangiomas and normal control group (p<0.001). To distinguish hemangiomas from malignant liver lesions, the “cut-off” ADC value of 1.800×10-3 mm2/s had a sensitivity of 97.4% and a specificity of 90.9%. To distinguish hemangioma from normal liver parenchyma the “cut-off” value of 1.858×10-3 mm2/s had a sensitivity of 97.4% and a specificity of 95.7%. To distinguish benign liver lesions from malignant liver lesions the “cut-off” value of 1.800×10-3 mm2/s had a sensitivity of 96.1% and a specificity of 90.0%. Conclusion: DWI and quantitative measurement of ADC values can be used in differential diagnosis of benign and malignant liver lesions and also in the diagnosis and differentiation of hemangiomas. When dynamic examination cannot distinguish cases with vascular metastasis and lesions from hemangioma, DWI and ADC values can be useful in the primary diagnosis and differential diagnosis. The technique does not require contrast material, so it can safely be used in patients with renal failure. Keywords:

Commercial enzyme-linked immunosorbent assay versus polymerase chain reaction for the diagnosis of chronic Chagas disease: a systematic review and meta-analysis

Chronic Chagas disease diagnosis relies on laboratory tests due to its clinical characteristics. The aim of this research was to review commercial enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) diagnostic test performance. Performance of commercial ELISA or PCR for the diagnosis of chronic Chagas disease were systematically searched in PubMed, Scopus, Embase, ISI Web, and LILACS through the bibliography from 1980-2014 and by contact with the manufacturers. The risk of bias was assessed with QUADAS-2. Heterogeneity was estimated with the I2 statistic. Accuracies provided by the manufacturers usually overestimate the accuracy provided by academia. The risk of bias is high in most tests and in most QUADAS dimensions. Heterogeneity is high in either sensitivity, specificity, or both. The evidence regarding commercial ELISA and ELISA-rec sensitivity and specificity indicates that there is overestimation. The current recommendation to use two simultaneous serological tests can be supported by the risk of bias analysis and the amount of heterogeneity but not by the observed accuracies. The usefulness of PCR tests are debatable and health care providers should not order them on a routine basis. PCR may be used in selected cases due to its potential to detect seronegative subjects.

A molecular platform for the diagnosis of multidrug-resistant and pre-extensively drug-resistant tuberculosis based on single nucleotide polymorphism mutations present in Colombian isolates of Mycobacterium tuberculosis

Developing a fast, inexpensive, and specific test that reflects the mutations present in Mycobacterium tuberculosis isolates according to geographic region is the main challenge for drug-resistant tuberculosis (TB) control. The objective of this study was to develop a molecular platform to make a rapid diagnosis of multidrug-resistant (MDR) and extensively drug-resistant TB based on single nucleotide polymorphism (SNP) mutations present in the rpoB, katG, inhA, ahpC, and gyrA genes from Colombian M. tuberculosis isolates. The amplification and sequencing of each target gene was performed. Capture oligonucleotides, which were tested before being used with isolates to assess the performance, were designed for wild type and mutated codons, and the platform was standardised based on the reverse hybridisation principle. This method was tested on DNA samples extracted from clinical isolates from 160 Colombian patients who were previously phenotypically and genotypically characterised as having susceptible or MDR M. tuberculosis. For our method, the kappa index of the sequencing results was 0,966, 0,825, 0,766, 0,740, and 0,625 for rpoB, katG, inhA, ahpC, and gyrA, respectively. Sensitivity and specificity were ranked between 90-100% compared with those of phenotypic drug susceptibility testing. Our assay helps to pave the way for implementation locally and for specifically adapted methods that can simultaneously detect drug resistance mutations to first and second-line drugs within a few hours.

Validation of the haemoglobin colour scale for screening blood donors in Malawi

Background In 2009 Malawi introduced a new protocol to screen potential blood donors for anaemia, using the WHO Haemoglobin Colour Scale (HCS) for initial screening. Published studies of the accuracy of the HCS to screen potential blood donors show varying levels of accuracy and opinion varies whether this is an appropriate screening test. The aim of the study was to assess the validity of the HCS, as a screening test, by comparison to HemoCue in potential blood donors in Malawi. Study design and Methods This was a blinded prospective study in potential blood donors aged over 18 years, at Malawi Blood Transfusion Service in Blantyre, Malawi. Capillary blood samples were analysed using the HCS and HemoCue, independent of each other. The sensitivity and specificity of correctly identifying ineligible blood donors (Hb≤12g/dL) were calculated. Results From 242 participants 234 (96.7%) were correctly allocated and 8 (3.3%), were wrongly allocated on the basis of the Haemoglobin Colour Scale (HCS) compared to HemoCue, all were subjects that were wrongly accepted as donors when their haemoglobin results were ≤12.0g/dL. This gave a sensitivity of 100% and specificity of 96.7% to detect donor eligibilty. The negative predictive value of the HCS was 100% but the positive predictive value to identify ineligible donors on the basis of anaemia was only 20%. Conclusions Initial screening with the HCS correctly predicts eligibility for blood donation in the majority of potential blood donors at considerable cost saving compared with use of HemoCue as the first line anaemia screening test, however, by this method a small number of anaemic patients were allowed to donate blood.

Polymerase chain reaction detection of Leishmania DNA in skin biopsy samples in Sri Lanka where the causative agent of cutaneous leishmaniasis is Leishmania donovani

Leishmania donovani is the known causative agent of both cutaneous (CL) and visceral leishmaniasis in Sri Lanka. CL is considered to be under-reported partly due to relatively poor sensitivity and specificity of microscopic diagnosis. We compared robustness of three previously described polymerase chain reaction (PCR) based methods to detect Leishmania DNA in 38 punch biopsy samples from patients presented with suspected lesions in 2010. Both, Leishmania genus-specific JW11/JW12 KDNA and LITSR/L5.8S internal transcribed spacer (ITS)1 PCR assays detected 92% (35/38) of the samples whereas a KDNA assay specific for L. donovani (LdF/LdR) detected only 71% (27/38) of samples. All positive samples showed a L. donovani banding pattern upon HaeIII ITS1 PCR-restriction fragment length polymorphism analysis. PCR assay specificity was evaluated in samples containing Mycobacterium tuberculosis , Mycobacterium leprae , and human DNA, and there was no cross-amplification in JW11/JW12 and LITSR/L5.8S PCR assays. The LdF/LdR PCR assay did not amplify M. leprae or human DNA although 500 bp and 700 bp bands were observed in M. tuberculosis samples. In conclusion, it was successfully shown in this study that it is possible to diagnose Sri Lankan CL with high accuracy, to genus and species identification, using Leishmania DNA PCR assays.

The Role of Lung Ultrasound in Diagnosis of Respiratory Distress Syndrome in Newborn Infants

Background: Respiratory distress syndrome (RDS) is one of the most common causes of neonatal respiratory failure and mortality. The risk of developing RDS decreases with both increasing gestational age and birth weight. Objectives: The aim of this study was to evaluate the value of lung ultrasound in the diagnosis of respiratory distress syndrome (RDS) in newborn infants. Materials and Methods: From March 2012 to May 2013, 100 newborn infants were divided into two groups: RDS group (50 cases) and control group (50 cases). According to the findings of chest x-ray, there were 10 cases of grade II RDS, 15 grade III cases, and 25 grade IV cases in RDS group. Lung ultrasound was performed at bedside by a single expert. The ultrasound indexes observed in this study included pleural line, A-line, B-line, lung consolidation, air bronchograms, bilateral white lung, interstitial syndrome, lung sliding, lung pulse etc. Results: In all of the infants with RDS, lung ultrasound consistently showed generalized consolidation with air bronchograms, bilateral white lung or alveolar-interstitial syndrome, pleural line abnormalities, A-line disappearance, pleural effusion, lung pulse, etc. The simultaneous demonstration of lung consolidation, pleural line abnormalities and bilateral white lung, or lung consolidation, pleural line abnormalities and A-line disappearance co-exists with a sensitivity and specificity of 100%. Besides, the sensitivity was 80% and specificity 100% of lung pulse for the diagnosis of neonatal RDS. Conclusions: This study indicates that using an ultrasound to diagnose neonatal RDS is accurate and reliable too. A lung ultrasound has many advantages over other techniques. Ultrasound is non-ionizing, low-cost, easy to operate, and can be performed at bedside, making this technique ideal for use in NICU.