Specificity Of Rapid Test Research Articles

Diagnostic utility of antigen detection rapid diagnostic tests for Covid-19: a systematic review and meta-analysis

BackgroundThe early detection of coronavirus disease (COVID-19) infection to improve disease management becomes the greatest challenge. Despite the high sensitivity of RT-PCR, not only it was reported that 20–67% of infected patients had false-negative results. Rapid diagnostic tests (RDTs) are widely used as a point-of-care test for SARS-CoV-2 detection in pharyngeal and blood specimens. It’s more appealing since it’s less time-consuming, doesn’t seem to be as expensive, and doesn’t need any specific training, but the poor sensitivity is the major limitation. Several reports indicated the rapid test of blood and pharyngeal samples has the same sensitivity as the RT-PCR, but some reports have lower sensitivity, especially in asymptomatic patients.MethodsIn the present survey, we investigate the eligible studies for the sensitivity and specificity of rapid tests and explore the factors that influence the result to help better diagnose COVID-19 infection. 20 studies met the inclusion criteria which imposed 33 different tests.ResultsOur findings showed the type of sample, the type of assay, the time of sampling, and the load of virus influence on the sensitivity of RDTs.ConclusionThis research extends our knowledge of how to improve the sensitivity of RDTs to better diagnose the infected patients to address the controlling COVID-19 pandemic.

Cholera Rapid Diagnostic Tests for the Detection of Vibrio cholerae O1: An Updated Meta-Analysis.

The rapid diagnosis of cholera contributes to adequate outbreak management. This meta-analysis assesses the diagnostic accuracy of cholera rapid tests (RDTs) to detect Vibrio cholerae O1. Methods: Systematic review and meta-analysis. We searched four databases (Medline, EMBASE, Google Scholar, and Web of Science up to 8 September 2021) for studies that evaluated cholera RDTs for the detection of V. cholerae O1 compared with either stool culture or polymerase chain reaction (PCR). We assessed the studies’ quality using the QUADAS-2 criteria. In addition, in this update, GRADE approach was used to rate the overall certainty of the evidence. We performed a bivariate random-effects meta-analysis to calculate the pooled sensitivity and specificity of cholera RDTs. Results: Overall, 20 studies were included in this meta-analysis. Studies were from Africa (n = 11), Asia (n = 7), and America (Haiti; n = 2). They evaluated eight RDTs (Crystal VC-O1, Crystal VC, Cholkit, Institut Pasteur cholera dipstick, SD Bioline, Artron, Cholera Smart O1, and Smart II Cholera O1). Using direct specimen testing, sensitivity and specificity of RDTs were 90% (95% CI, 86 to 93) and 86% (95% CI, 81 to 90), respectively. Cholera Sensitivity was higher in studies conducted in Africa [92% (95% CI, 89 to 94)] compared with Asia [82% (95% CI, 77 to 87)]. However, specificity [83% (95% CI, 71 to 91)] was lower in Africa compared with Asia [90% (95% CI, 84 to 94)]. GRADE quality of evidence was estimated as moderate. Conclusions: Against culture or PCR, current cholera RDTs have moderate sensitivity and specificity for detecting Vibrio cholerae O1.

The Value of Rapid Antigen Tests for Identifying Carriers of Viable SARS-CoV-2.

The search for effective methods to detect patients who excrete a viable virus is one of the urgent tasks of modern biomedicine. In the present study, we examined the diagnostic value of two antigen tests, BIOCREDIT COVID-19 Ag (RapiGEN Inc., Anyang, Korea) and SGTI-flex COVID-19 Ag (Sugentech Inc., Cheongju, Korea), for their diagnostic value in identifying patients who excrete viable SARS-CoV-2. As part of the study, we examined samples from 106 patients who had just been admitted to the hospital and who had undergone quantitative RT-PCR and assessment of viability of SARS-CoV-2 using cell culture. Assessment of the tests’ value for detecting samples containing viable virus showed high sensitivity for both tests. Sensitivity was 78.6% (95% CI, from 49.2% to 95.3%) for SGTI-flex COVID-19 Ag and 100% (95% CI, from 76.8% to 100%) for Biocredit COVID-19 Ag. The specificity of rapid tests was significantly higher than that of RT-PCR and was 66.3% (95% CI, from 55.7% to 75.8%) and 67.4% (95% CI, from 56.8% to 76.8%) for SGTI-flex COVID-19 Ag and Biocredit COVID-19 Ag versus 30.4% (95% CI, from 21.3% to 40.9%) obtained for PCR. Thus, for tasks of identifying viable SARS-CoV-2 during screening of conditionally healthy people, as well as monitoring those quarantined, rapid tests show significantly better results.

Sensitivity and Specificity of a COVID-19 Lateral Flow Immunoassay Compared to RT-PCR in Pregnant Womenat Arifin Achmad General Hospital Pekanbaru, Indonesia

Coronavirus disease 2019 (COVID-19) is significant global treat including to pregnant woman in Indonesia.A point-of-care diagnostic tool that is able to early diagnose and hasa good sensitivity and specificity iscritical during the pandemic. The aim of this study was to describe the clinical, laboratory and outcomesof pregnant women with presumptive COVID-19 and to compare the sensitivity and specificity betweenCOVID-19 rapid test (lateral flow immunoassay) and real-time reverse transcription polymerase chainreaction (RT-PCR). Pregnant women with presumptive COVID-19 symptoms were recruited at ArifinAchmad General Hospital between April 2020 and December 2020. Demographic and clinical data werecollected and patients were tested with COVID-19 rapid test as well as RT-PCR. Analyze was conducted todetermine the sensitivity and specificity. We included 120 patients with presumptive COVID-19 of which48 (40%) and 72 (60%) of patients were reactive for IgM and IgG antibody anti severe acute respiratorysyndrome coronavirus 2 (SARS-CoV-2), respectively and 51 (42.5%) were reactive for both IgM and IgG.The sensitivity and the specificity of rapid test was 64.0% and 33.3%, respectively. The positive and negativepredictive value was 61.5% and 35.7%, respectively. In conclusion, lateral flow immunoassay-based rapidtest has relatively low sensitivity and specificity in diagnosing COVID-19 in pregnant women.

Frequency of Hepatitis C Virus in Diagnosed Tuberculosis Cases

Background: The frequency of hepatitis C virus infection along with tuberculosis has not been widely investigated and very low statistics on rates of hepatitis C virus co-infection in tuberculosis patients. Hepatotoxicity is the major side effect of anti-tuberculosis therapy hepatitis HCVliver disease elevates the chances of hepatotoxicity up-to five folds. Aim: To see the frequency of Hepatitis Cvirus infection amongst people with diagnosed Tuberculosis using gene X-pert technique. To evaluate the factors associated with HCVinfection in patients with MTBtuberculosis and to determine sensitivity and specificity of the tests. Study design: Comparative analytical study. Place and duration of study: Pathology Department, Civil Hospital Mirpur Khas Sindh from 1stJanuary 2017 to 31st December 2018. Methodology: Three hundred and thirteen patients of tuberculosis diagnosed by Genexpert included while testing hepatitis C virus using immunochromotography rapid test technique, enzyme linked immunosorbent assay method and polymerase chain reaction test for confirmation. Results:Higher frequency of tuberculosis infection in males 57.8%, 42.5% between 20-39 years and 22% of hepatitis C virus infection in tuberculosis patients.Sensitivity of rapid test and enzyme-linked immunosorbent assay was 79% and 96% respectively while the specificity of rapid test and enzyme-linked immunosorbent assay was 91% and 99% respectively. Conclusion: The high frequency of hepatitis C virus co-infection was found among tuberculosis cases in Mirpur Khas Division Sindh. Enzyme-linked immunosorbent assay method is more accurate, reliable as compared to rapid immunochromatographytest for hepatitis C virus and polymerase chain reaction is still gold standard. Keywords: TB, Hepatitis C virus, Mycobacterium tuberculosis,, PCR, Genexpert, Rapid test

The Prevalence of Hepatitis B, Hepatitis C and Human Immunodeficiency Viral Infections Among a Large Population of Afghans

Background: Viral infections are a public health problem. Objectives: We would like to evaluate the seroprevalence of hepatitis B, C, and human immunodeficiency virus infections (HIV) in a large sample of the Afghanistan population in Kabul. Methods: In total, 196516 Afghani citizens went to Fateme-al-Zahra clinic to perform obligatory checkup for traveling to Iran. The serum samples were primarily checked by rapid tests for HBV, HCV, and HIV, and in case of positive results, a commercial ELISA kit used as the confirmatory test. Results: Out of 196516 participants, 153763(78%) were men and 42753 (22%) were women. The seroprevalence of HBV, HCV, and HIV infections was 1.23% (2430), 0.13% (265) and 0.018% (16), respectively. The prevalence of HCV and HIV was significantly higher in males than females (m/f: 0.097%/0.037% vs. m/f: 0.008%/0%, respectively; P < 0.05). The simultaneous co-infection of HBV-HCV and HBV-HIV was 0.004% and 0.0005 %, respectively. Conclusions: This study showed a low prevalence of HBV, HCV, and HIV among the study group. Considering the selection bias, sensitivity, and specificity of rapid tests, the real prevalence expected to be quite higher. Proper strategies to improve the social awareness and implement preventive vaccination for HBV can decrease the incidence of these infections.

SARS-Cov-2 infection: Response of human immune system and possible implications for the rapid test and treatment

The new coronavirus outbreak is an ongoing pandemic that is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The new coronavirus SARS-Cov-2 belongs to the subfamily of β–coronaviruses and shares 79.5% of the genetic sequence of SARS-CoV, the causative agent of the epidemic that started in 2002 and ended in 2004.Considering the clinical impact of the new outbreak, it is highly important to study the potential responses of the human immune system during the SARS-CoV-2 infection as well as the role of virus-specific T cells and by B-lymphocytes. Moreover, specific data on the production of IgG and IgM is crucial to allow the rapid identification of the infection. In this paper we also described the importance of sensitive and specific rapid test for SARS-CoV-2. Indeed, this test represents an important immunological tool aimed at identifying the precise phase of the infection in order to undertake a more appropriate pharmacological treatment. Lastly, we provided an overview of pharmacological treatments aimed to reduce inflammatory processes underlying the infection and the need for the discovery of a new vaccine against SARS-CoV-2.

A comparison of three diagnostic platforms for the detection of influenza A and B in children

Background: Viral flu is the predominant cause of hospitalization in young children, which invariably leads to enhanced morbidity and mortality in children in developing countries. Initial treatment of viral flu is based on presumptive diagnosis. Bedside testing is not common in clinical settings because of variable sensitivity and specificity of rapid tests in different settings. Methods: To address this issue, we evaluated the performance of Binax influenza A/B rapid testing kit against two robust molecular platforms (quantitative real-time polymerase chain reaction [qRT-PCR] and TaqMan array card [TAC]) in 24 nasopharyngeal (NP) swabs, collected from children under 5 years of age. Results: Binax was found to be less sensitive (56%), but 100% specific compared to qRT-PCR (100%) and TAC (>100%). Using TAC cards, 75% of samples were found to be coinfected with other bacterial and viral targets. Conclusion: Binax flu is suitable for bedside testing in clinical and community settings. The negative results of Binax should be interpreted with caution and confirmed by rapid molecular tests.

Would a good screening test increase the effectiveness of border screening for influenza control?

This article discusses the role of border screening in influenza control and places influenza screening in the context of the whole screening pathway. We conclude that while having a sensitive and specific rapid test for influenza antibody will improve the border screening process, it will have limited impact on the overall effectiveness of the border screening because only a proportion of infected cases present with symptoms at the border.

Prospective study to evaluate the number and the location of biopsies in rapid urease test for diagnosis of Helicobacter Pylori

Helicobacter pylori (H. pylori) can cause a wide variety of illnesses such as peptic ulcer disease, gastric adenocarcinoma and mucosa-associated lymphoid tissue (MALT) lymphoma. The diagnosis and eradication of H. pylori are crucial. The diagnosis of H. pylori is usually based on the rapid urease test (RUT) and gastric antral biopsy for histology. The aim of this study is to evaluate the numbers of needed biopsies and their location (antrum/fundus) to obtain optimal result for the diagnosis of H. pylori. Three hundred fifty consecutive patients were recruited, 210 fulfill the inclusion criteria and had nine gastric biopsies for the detection of H. pylori infection: two antral for the first RUT (RUT1), one antral and one fundic for the second (RUT2), one antral for the third (RUT3) and two antral with two fundic for histology (HES, Giemsa, PAS). The reading of the 3 types of RUT was performed at 1 hour, 3 hours and 24 hours and biopsies were read by two experienced pathologists not informed about the result of RUT. Results of RUT were considered positive if H. pylori was found on histology of at least one biopsy. The RUT1 at 1h, 3h and 24h has a sensitivity of 72%, 82% and 89% and a specificity of 100%, 99% and 87% respectively. The positive predictive value (PPV) was 100%, 99% and 85% respectively and the negative predictive value (NPV) of 81%, 87% and 90%. The RUT2 at 1h, 3h and 24h, respectively, had a sensitivity of 86%, 87% and 91% and a specificity of 99%, 97% and 90%. The PPV was 99%, 96% and 88% and NPV of 89%, 90%, 94%. The RUT3 at 1h, 3h and 24h, respectively, had a sensitivity of 70%, 74% and 84% and a specificity of 99%, 99% and 94%. The PPV was 99%, 99% and 92% and NPV of 79%, 81% and 87%. The best sensitivity and specificity were obtained for RUT1 read at 3h, for RUT2 read 1h and 3h, and the RUT3 read at 24h.This study demonstrates that the best sensitivity and specificity of rapid test for urease is obtained when fundic plus antral biopsy specimens are used with a reading time at 3 hours.

1484Detection of Respiratory Syncytial (RSV) and Influenza Viruses in Children with WHO Defined Pneumonia and Controls from Oshikhandass Village, Gilgit-Baltistan, Northern Pakistan from 2012-2014; Sensitivity and Specificity of Rapid Tests vs PCR

1484Detection of Respiratory Syncytial (RSV) and Influenza Viruses in Children with WHO Defined Pneumonia and Controls from Oshikhandass Village, Gilgit-Baltistan, Northern Pakistan from 2012-2014; Sensitivity and Specificity of Rapid Tests vs PCR

Rapid tests for the diagnosis of visceral leishmaniasis in patients with suspected disease.

BackgroundThe diagnosis of visceral leishmaniasis (VL) in patients with fever and a large spleen relies on showing Leishmania parasites in tissue samples and on serological tests. Parasitological techniques are invasive, require sophisticated laboratories, consume time, or lack accuracy. Recently, rapid diagnostic tests that are easy to perform have become available.ObjectivesTo determine the diagnostic accuracy of rapid tests for diagnosing VL in patients with suspected disease presenting at health services in endemic areas.Search methodsWe searched MEDLINE, EMBASE, LILACS, CIDG SR, CENTRAL, SCI‐expanded, Medion, Arif, CCT, and the WHO trials register on 3 December 2013, without applying language or date limits.Selection criteriaThis review includes original, phase III, diagnostic accuracy studies of rapid tests in patients clinically suspected to have VL. As reference standards, we accepted: (1) direct smear or culture of spleen aspirate; (2) composite reference standard based on one or more of the following: parasitology, serology, or response to treatment; and (3) latent class analysis.Data collection and analysisTwo review authors independently extracted data and assessed quality of included studies using the QUADAS‐2 tool. Discrepancies were resolved by a third author. We carried out a meta‐analysis to estimate sensitivity and specificity of rapid tests, using a bivariate normal model with a complementary log‐log link function. We analysed each index test separately. As possible sources of heterogeneity, we explored: geographical area, commercial brand of index test, type of reference standard, disease prevalence, study size, and risk of bias (QUADAS‐2). We also undertook a sensitivity analysis to assess the influence of imperfect reference standards.Main resultsTwenty‐four studies containing information about five index tests (rK39 immunochromatographic test (ICT), KAtex latex agglutination test in urine, FAST agglutination test, rK26 ICT, and rKE16 ICT) recruiting 4271 participants (2605 with VL) were included. We carried out a meta‐analysis for the rK39 ICT (including 18 studies; 3622 participants) and the latex agglutination test (six studies; 1374 participants). The results showed considerable heterogeneity. For the rK39 ICT, the overall sensitivity was 91.9% (95% confidence interval (95% CI) 84.8 to 96.5) and the specificity 92.4% (95% CI 85.6 to 96.8). The sensitivity was lower in East Africa (85.3%; 95% CI 74.5 to 93.2) than in the Indian subcontinent (97.0%; 95% CI 90.0 to 99.5). For the latex agglutination test, overall sensitivity was 63.6% (95% CI 40.9 to 85.6) and specificity 92.9% (95% CI 76.7 to 99.2).Authors' conclusionsThe rK39 ICT shows high sensitivity and specificity for the diagnosis of visceral leishmaniasis in patients with febrile splenomegaly and no previous history of the disease, but the sensitivity is notably lower in east Africa than in the Indian subcontinent. Other rapid tests lack accuracy, validation, or both.15 April 2019Update pendingStudies awaiting assessmentThe CIDG is currently examining a new search conducted in April 2019 for potentially relevant studies. These studies have not yet been incorporated into this Cochrane Review.

Optimal Triage Test Characteristics to Improve the Cost-Effectiveness of the Xpert MTB/RIF Assay for TB Diagnosis: A Decision Analysis

BackgroundHigh costs are a limitation to scaling up the Xpert MTB/RIF assay (Xpert) for the diagnosis of tuberculosis in resource-constrained settings. A triaging strategy in which a sensitive but not necessarily highly specific rapid test is used to select patients for Xpert may result in a more affordable diagnostic algorithm. To inform the selection and development of particular diagnostics as a triage test we explored combinations of sensitivity, specificity and cost at which a hypothetical triage test will improve affordability of the Xpert assay.MethodsIn a decision analytical model parameterized for Uganda, India and South Africa, we compared a diagnostic algorithm in which a cohort of patients with presumptive TB received Xpert to a triage algorithm whereby only those with a positive triage test were tested by Xpert.FindingsA triage test with sensitivity equal to Xpert, 75% specificity, and costs of US$5 per patient tested reduced total diagnostic costs by 42% in the Uganda setting, and by 34% and 39% respectively in the India and South Africa settings. When exploring triage algorithms with lower sensitivity, the use of an example triage test with 95% sensitivity relative to Xpert, 75% specificity and test costs $5 resulted in similar cost reduction, and was cost-effective by the WHO willingness-to-pay threshold compared to Xpert for all in Uganda, but not in India and South Africa. The gain in affordability of the examined triage algorithms increased with decreasing prevalence of tuberculosis among the cohort.ConclusionsA triage test strategy could potentially improve the affordability of Xpert for TB diagnosis, particularly in low-income countries and with enhanced case-finding. Tests and markers with lower accuracy than desired of a diagnostic test may fall within the ranges of sensitivity, specificity and cost required for triage tests and be developed as such.

Les thrombocytopénies induites par l’héparine : données récentes

Despite less frequent, heparin-induced thrombocytopenia (HIT) remains a severe complication of treatment with heparin, and is important to diagnose and manage appropriately. HIT results from an atypical immune response to heparin, with the synthesis of IgG antibodies specific to heparin-modified platelet factor 4 (PF4) which activate platelets, leukocytes and the endothelium. This activation explains that low platelet count is associated with thrombotic events in 50% of patients. The diagnosis of HIT is sometimes evoked because of atypical manifestations (i.e. cutaneous necrosis, amnesia, hypotension or dyspnea following intravenous injection of heparin). Biological assays are always necessary to confirm HIT in case of clinical suspicion, and specific rapid tests are now available for detecting anti-PF4 antibodies. However, their specificity is poor and functional assays such as serotonin release assay or platelet aggregation test are often necessary. Argatroban that is a direct antithrombin drug can be used in patients with severe renal failure and will be preferred to danaparoid sodium in this situation. Fondaparinux is not licensed for treating confirmed HIT and can only be used in case of suspicion. The early detection of HIT is based on the monitoring of platelet count recommended in surgical patients receiving a low molecular weight heparin and in all patients treated with unfractionated heparin.

Prognostic Value of Rapid Test for Diagnosis of Dengue in Nepalese Patients during 2010 Epidemic

Dengue is an emerging vector borne disease in Nepal and rapid diagnostic test is important for early diagnosis of the disease. The aim of the study was to evaluate the diagnostic accuracy of commonly used rapid immunochromatographic test kit in Nepal during 2010 dengue epidemic and to assess disease burden of dengue. A total of 131 acute and nonacute serum samples were collected during recent epidemic of dengue in 2010 from clinically suspected Nepalese patients of different hospitals. Rapid immunochromatographic test kit was used for early diagnosis and enzyme immunosorbent was chosen as a reference assay. The sensitivity and specificity of rapid test was 70% and 76.54% respectively whereas the prevalence of the disease was 38.17%. The odds ratio for males was 1.8 however; the association with the disease was statistically not significant. The diagnostic accuracy of rapid immunochromatographic test for dengue diagnosis was low (k=0.46). So, it should be substituted by highly sensitive test device for prompt diagnosis and health personnel should consider appropriate timing of sample collection for better performance of rapid test.

P3-S3.08 Sensitivity and specificity of rapid HIV testing in a community setting

BackgroundIt was estimated in 2005 that 13% of men who have sex with men (MSM) in Montréal were HIV-positive, and that 23% of these were not aware of their diagnosis....

Rapid HIV Testing in a Southeastern Emergency Department Serving a Semiurban-Semirural Adolescent and Adult Population

We determine the feasibility and yield of universal opt-out HIV screening among adolescents and adults in a southeastern emergency department (ED) serving a semiurban-semirural population. Individuals aged 13 to 64 years who visited the ED during specified hours received the OraQuick rapid HIV test (administered by trained counselors) if they did not opt out. Western blot was used to confirm reactive results. Patients were excluded if they had a history of HIV, had been tested within the past year, were physically or mentally incapacitated, did not understand their right to opt out, or did not speak English or Spanish. Basic demographic information was analyzed by using standard descriptive statistics. Measures of diagnostic test performance were calculated for all valid tests. From March 2008 through August 2009, 91% (n=8,493) of eligible patients accepted testing, and results were valid. Of 41 reactive results, 35 were confirmed HIV positive, 2 were indeterminate by Western blot, and 4 were false positive. Blacks accounted for the largest percentage (0.65%) of newly detected infections, and the percentage among black men (1%) was more than twice the percentage among black women (0.42%). Rapid-test specificity was estimated at 99.95% (95% confidence interval 99.88% to 99.98%). Nearly 75% of patients confirmed as HIV positive kept their first HIV clinic appointment. High rates of acceptance of testing in an ED and linkage to HIV care for adolescents and adults with newly detected infection can be achieved by using opt-out testing and trained HIV counselors.

Occurrence of tetracycline, chlortetracycline, and oxytetracycline residues in raw cow's milk

The objective of this study was the detection of tetracycline, chlortetracycline and oxytetracycline residues in raw cow’s milk. When analysing bulk milk (<i>n</i> = 57) and tanker trailer’a (<i>n</i> = 113) samples, two methods were used simultaneously: a specific rapid test Milk Tetrasensor Kit and high performance liquid chromatography (HPLC) with ultraviolet detection and isocratic elution. For HPLC analysis, Breeze (Waters, USA), a liquid chromatographic system, was used. The samples underwent solid phase extraction before the HPLC analysis. The Nova Pack C8 column (3.9 × 150 mm, 4 μm, Waters) and mobile phase (0.8 ml/min) consisting of acetonitrile, methanol, and 0.05 mol/l of oxalic acid in a 13:13:74 ratio were used. None of the samples analysed with the use of the specific rapid test displayed the presence of tetracycline antibiotics. In all of the samples analysed by means of HPLC, low concentrations of tetracycline antibiotics residues were detected. None of the samples displayed the presence of chlortetracycline. All of the analysed samples displayed residues of tetracycline. Oxytetracycline residues were detected only in 50.6% of analysed samples.

Detection of Clostridium difficile infection: a suggested laboratory diagnostic algorithm

Currently, the diagnosis of Clostridium difficile infection (CDI) relies on the detection of toxins A and B in faeces but the sensitivity of these tests has been questioned, particularly in advanced disease. In this context, additional methods to enhance the diagnosis of C. difficile have been investigated. In this study, 1007 faecal samples are tested using toxigenic culture, an immunoassay for toxins AB and the C. difficile-specific glutamate dehydrogenase (GDH) test. Samples positive by any of the above tests are evaluated for the presence of faecal lactoferrin as an indicator of intestinal inflammation. Patients with evidence of inflammation but with negative toxin AB tests are followed up to assess clinical outcome. The toxin AB test was positive in 35 samples (3.4%), while 121 (12%) samples were culture-positive, 87 (8.6%) of which were toxigenic. Glutamate dehydrogenase proved to be a sensitive and specific marker of C. difficile with a negative predictive value of 99.3% (95% CI: 0.98–1.00). Faecal lactoferrin was positive in 52/129 (40.3%) samples tested. A cohort of 15 patients with a negative faecal toxin AB and a positive lactoferrin test was C. difficile culture-positive with a toxigenic isolate; clinically, all had advanced CDI. All demonstrated faecal toxin between five and 41 days later on repeat testing. It is suggested that a two-step algorithm be used to include screening faecal samples for GDH, with positive samples tested for faecal toxin AB and lactoferrin. Patients who present with a negative faecal toxin AB test and a positive lactoferrin test were serially tested for faecal toxin AB every five to seven days until a diagnosis was established. More sensitive tests than enzyme-linked immunosorbent assay (ELISA) for the detection of faecal toxin, or the use of a rapid specific test for the presence of a toxigenic strain, must be considered in such patients.

Papel do teste de detecção rápida do antígeno do estreptococcus beta-hemolítico do grupo a em pacientes com faringoamigdalites

O Streptococcus beta-hemolítico do grupo A (SGA) é o agente etiológico mais comum das faringoamigdalites (FA). O diagnóstico etiológico correto e tratamento adequado evitam complicações supurativas e não-supurativas da faringoamigdalite estreptocócica, entretanto, métodos clínicos de diagnóstico não são confiáveis. Os métodos rápidos de detecção do antígeno do SGA podem ser utilizados no diagnóstico deste agente e evitar uso indevido de antibióticos. OBJETIVOS: Os autores objetivaram avaliar a sensibilidade e especificidade dos testes rápidos para detecção do antígeno do SGA em nosso meio. FORMA DE ESTUDO: Clínico prospectivo. METODOLOGIA: Oitenta e um pacientes com faringoamigdalite aguda, atendidos no PS-ORL do Hospital das Clínicas da FMUSP, no período de maio de 2001 a abril de 2002, foram submetidos a duas coletas simultâneas de material de orofaringe com swabs. O teste rápido de detecção do SGA foi confrontado com a cultura em placa agar-sangue ("gold standard" para o diagnóstico etiológico). RESULTADOS: De 81 pacientes, 56% tiveram teste rápido positivo e 44% negativo; 40.7% apresentaram crescimento de SGA na cultura; a sensibilidade e especificidade do teste rápido foram, respectivamente, 93,9% e 68,7%. O valor preditivo negativo e positivo foram, respectivamente, 94,2% e 67,4%. CONCLUSÕES: A alta sensibilidade do exame permite utilizá-lo com intuito de identificar pacientes com SGA. Os testes de detecção rápida do antígeno estreptocócico se mostraram uma importante arma coadjuvante no diagnóstico etiológico das faringoamigdalites.