Smear plus Detect-TB for a sensitive diagnosis of pulmonary tuberculosis: a cost-effectiveness analysis in an incarcerated population.

BACKGROUND: Prison conditions can favor the spread of tuberculosis (TB). This study aimed to evaluate in a Brazilian prison: the performance and accuracy of smear, culture and Detect-TB; performance of smear plus culture and smear plus Detect-TB, according to different TB prevalence rates; and the cost-effectiveness of these procedures for pulmonary tuberculosis (PTB) diagnosis. METHODS: This paper describes a cost-effectiveness study. A decision analytic model was developed to estimate the costs and cost-effectiveness of five routine diagnostic procedures for diagnosis of PTB using sputum specimens: a) Smear alone, b) Culture alone, c) Detect-TB alone, d) Smear plus culture and e) Smear plus Detect-TB. The cost-effectiveness ratio of costs were evaluated per correctly diagnosed TB case and all procedures costs were attributed based on the procedure costs adopted by the Brazilian Public Health System. RESULTS: A total of 294 spontaneous sputum specimens from patients suspected of having TB were analyzed. The sensibility and specificity were calculated to be 47% and 100% for smear; 93% and 100%, for culture; 74% and 95%, for Detect-TB; 96% and 100%, for smear plus culture; and 86% and 95%, for smear plus Detect-TB. The negative and positive predictive values for smear plus Detect-TB, according to different TB prevalence rates, ranged from 83 to 99% and 48 to 96%, respectively. In a cost-effectiveness analysis, smear was both less costly and less effective than the other strategies. Culture and smear plus culture were more effective but more costly than the other strategies. Smear plus Detect-TB was the most cost-effective method. CONCLUSIONS: The Detect-TB evinced to be sensitive and effective for the PTB diagnosis when applied with smear microscopy. Diagnostic methods should be improved to increase TB case detection. To support rational decisions about the implementation of such techniques, cost-effectiveness studies are essential, including in prisons, which are known for health care assessment problems.

Comparison of two laboratory-developed PCR methods for the diagnosis of pulmonary tuberculosis in Brazilian patients with and without HIV infection.

BACKGROUND: Direct smear examination with Ziehl-Neelsen (ZN) staining for the diagnosis of pulmonary tuberculosis (PTB) is cheap and easy to use, but its low sensitivity is a major drawback, particularly in HIV seropositive patients. As such, new tools for laboratory diagnosis are urgently needed to improve the case detection rate, especially in regions with a high prevalence of TB and HIV. OBJECTIVE: To evaluate the performance of two in house PCR (Polymerase Chain Reaction): PCR dot-blot methodology (PCR dot-blot) and PCR agarose gel electrophoresis (PCR-AG) for the diagnosis of Pulmonary Tuberculosis (PTB) in HIV seropositive and HIV seronegative patients. METHODS: A prospective study was conducted (from May 2003 to May 2004) in a TB/HIV reference hospital. Sputum specimens from 277 PTB suspects were tested by Acid Fast Bacilli (AFB) smear, Culture and in house PCR assays (PCR dot-blot and PCR-AG) and their performances evaluated. Positive cultures combined with the definition of clinical pulmonary TB were employed as the gold standard. RESULTS: The overall prevalence of PTB was 46% (128/277); in HIV+, prevalence was 54.0% (40/74). The sensitivity and specificity of PCR dot-blot were 74% (CI 95%; 66.1%-81.2%) and 85% (CI 95%; 78.8%-90.3%); and of PCR-AG were 43% (CI 95%; 34.5%-51.6%) and 76% (CI 95%; 69.2%-82.8%), respectively. For HIV seropositive and HIV seronegative samples, sensitivities of PCR dot-blot (72% vs 75%; p=0.46) and PCR-AG (42% vs 43%; p=0.54) were similar. Among HIV seronegative patients and PTB suspects, ROC analysis presented the following values for the AFB smear (0.837), Culture (0.926), PCR dot-blot (0.801) and PCR-AG (0.599). In HIV seropositive patients, these area values were (0.713), (0.900), (0.789) and (0.595), respectively. CONCLUSION: Results of this study demonstrate that the in house PCR dot blot may be an improvement for ruling out PTB diagnosis in PTB suspects assisted at hospitals with a high prevalence of TB/HIV.

Genotype®MTBDRplus and Xpert®MTB/RIF in the diagnosis of tuberculosis and resistant tuberculosis: cost analysis in a tertiary referral hospital.

INTRODUCTION: The present study sought to assess the mean and activity based cost (ABC) of the laboratory diagnosis for tuberculosis through the application of conventional and molecular techniques-Xpert®MTB/RIF and Genotype®MTBDRplus-in a tertiary referral hospital in Brazil. METHODS: The mean cost and ABC formed the basis for the cost analysis of the TB laboratory diagnosis. RESULTS: The mean cost and ABC were US$ 4.00 and US$ 3.24, respectively, for a bacilloscopy; US$ 6.73 and US$ 5.27 for a Lowenstein-Jensen (LJ) culture; US$ 105.42 and US$ 76.56 for a drug sensitivity test (DST)-proportions method (PM) in LJ; US$ 148.45 and US$ 136.80 for a DST-BACTECTM MGITTM 960 system; US$ 11.53 and US$ 9.89 for an Xpert®MTB/RIF; and US$ 84.21 and US$ 48.38 for a Genotype®MTBDRplus. CONCLUSIONS: The mean cost and ABC proved to be good decision-making parameters in the diagnosis of TB and MDR-TB. The effective implementation of algorithms will depend on the conditions at each location.

Cost-effectiveness analysis of PCR for the rapid diagnosis of pulmonary tuberculosis.

BACKGROUND: Tuberculosis is one of the most prominent health problems in the world, causing 1.75 million deaths each year. Rapid clinical diagnosis is important in patients who have co-morbidities such as Human Immunodeficiency Virus (HIV) infection. Direct microscopy has low sensitivity and culture takes 3 to 6 weeks 123. Therefore, new tools for TB diagnosis are necessary, especially in health settings with a high prevalence of HIV/TB co-infection. METHODS: In a public reference TB/HIV hospital in Brazil, we compared the cost-effectiveness of diagnostic strategies for diagnosis of pulmonary TB: Acid fast bacilli smear microscopy by Ziehl-Neelsen staining (AFB smear) plus culture and AFB smear plus colorimetric test (PCR dot-blot).From May 2003 to May 2004, sputum was collected consecutively from PTB suspects attending the Parthenon Reference Hospital. Sputum samples were examined by AFB smear, culture, and PCR dot-blot. The gold standard was a positive culture combined with the definition of clinical PTB. Cost analysis included health services and patient costs. RESULTS: The AFB smear plus PCR dot-blot require the lowest laboratory investment for equipment (US$ 20,000). The total screening costs are 3.8 times for AFB smear plus culture versus for AFB smear plus PCR dot blot costs (US$ 5,635,760 versus US$ 1,498, 660). Costs per correctly diagnosed case were US$ 50,773 and US$ 13,749 for AFB smear plus culture and AFB smear plus PCR dot-blot, respectively. AFB smear plus PCR dot-blot was more cost-effective than AFB smear plus culture, when the cost of treating all correctly diagnosed cases was considered. The cost of returning patients, which are not treated due to a negative result, to the health service, was higher in AFB smear plus culture than for AFB smear plus PCR dot-blot, US$ 374,778,045 and US$ 110,849,055, respectively. CONCLUSION: AFB smear associated with PCR dot-blot associated has the potential to be a cost-effective tool in the fight against PTB for patients attended in the TB/HIV reference hospital.

PCR colorimetric dot-blot assay and clinical pretest probability for diagnosis of Pulmonary Tuberculosis in smear-negative patients.

BACKGROUND: Smear-negative pulmonary tuberculosis (SNPTB) accounts for 30% of Pulmonary Tuberculosis (PTB) cases reported annually in developing nations. Polymerase chain reaction (PCR) may provide an alternative for the rapid detection of Mycobacterium tuberculosis (MTB); however little data are available regarding the clinical utility of PCR in SNPTB, in a setting with a high burden of TB/HIV co-infection. METHODS: To evaluate the performance of the PCR dot-blot in parallel with pretest probability (Clinical Suspicion) in patients suspected of having SNPTB, a prospective study of 213 individuals with clinical and radiological suspicion of SNPTB was carried out from May 2003 to May 2004, in a TB/HIV reference hospital. Respiratory specialists estimated the pretest probability of active disease into high, intermediate, low categories. Expectorated sputum was examined by direct microscopy (Ziehl-Neelsen staining), culture (Lowenstein Jensen) and PCR dot-blot. Gold standard was based on culture positivity combined with the clinical definition of PTB. RESULTS: In smear-negative and HIV subjects, active PTB was diagnosed in 28.4% (43/151) and 42.2% (19/45), respectively. In the high, intermediate and low pretest probability categories active PTB was diagnosed in 67.4% (31/46), 24% (6/25), 7.5% (6/80), respectively. PCR had sensitivity of 65% (CI 95%: 50%-78%) and specificity of 83% (CI 95%: 75%-89%). There was no difference in the sensitivity of PCR in relation to HIV status. PCR sensitivity and specificity among non-previously TB treated and those treated in the past were, respectively: 69%, 43%, 85% and 80%. The high pretest probability, when used as a diagnostic test, had sensitivity of 72% (CI 95%:57%-84%) and specificity of 86% (CI 95%:78%-92%). Using the PCR dot-blot in parallel with high pretest probability as a diagnostic test, sensitivity, specificity, positive and negative predictive values were: 90%, 71%, 75%, and 88%, respectively. Among non-previously TB treated and HIV subjects, this approach had sensitivity, specificity, positive and negative predictive values of 91%, 79%, 81%, 90%, and 90%, 65%, 72%, 88%, respectively. CONCLUSION: PCR dot-blot associated with a high clinical suspicion may provide an important contribution to the diagnosis of SNPTB mainly in patients that have not been previously treated attended at a TB/HIV reference hospital.

Low prevalence of primary antiretroviral resistance mutations and predominance of HIV-1 clade C at polymerase gene in newly diagnosed individuals from south Brazil.

We describe preliminary molecular characterization of HIV-1 pol from 108 consecutive HIV seropositive users of a Voluntary Counseling and Testing (VCT) site of Porto Alegre city, the major metropolitan area in the south of Brazil. Protease and partial reverse transcriptase regions were retrotranscribed from plasma HIV-1 RNA and sequenced after direct nested PCR. Principal antiretroviral resistance mutations (ARM) were observed in 3% of the samples, two cases with K103N and one with M41L, L210W and T215Y, all in HIV-1 clade B infected men. At protease region, no principal mutations were observed, but polymorphisms at secondary codons were frequent. Contrary to other areas in the country where clade B dominates, HIV-1 clade C genomes predominated in this study (58%), clade B (32%) and clade F1 (3%). Of the genomes clustering in clade C, almost half (43%) had a small clade B segment at reverse transcriptase, forming a sub-cluster within clade C with a similar recombinant structure and carrying new amino acid signatures. Other mosaic genomes were also observed (7%). The low prevalence of resistance mutations is consistent with previous observations at this geographical location but the high frequency of HIV-1 clade C and CB mosaics seems pre-eminent and warns close monitoring.

Genotype®MTBDRplus and Xpert®MTB/RIF in the diagnosis of tuberculosis and resistant tuberculosis: cost analysis in a tertiary referral hospital

Abstract INTRODUCTION: The present study sought to assess the mean and activity based cost (ABC) of the laboratory diagnosis for tuberculosis through the application of conventional and molecular techniques-Xpert®MTB/RIF and Genotype®MTBDRplus-in a tertiary referral hospital in Brazil. METHODS: The mean cost and ABC formed the basis for the cost analysis of the TB laboratory diagnosis. RESULTS: The mean cost and ABC were US$ 4.00 and US$ 3.24, respectively, for a bacilloscopy; US$ 6.73 and US$ 5.27 for a Lowenstein-Jensen (LJ) culture; US$ 105.42 and US$ 76.56 for a drug sensitivity test (DST)-proportions method (PM) in LJ; US$ 148.45 and US$ 136.80 for a DST-BACTECTM MGITTM 960 system; US$ 11.53 and US$ 9.89 for an Xpert®MTB/RIF; and US$ 84.21 and US$ 48.38 for a Genotype®MTBDRplus. CONCLUSIONS: The mean cost and ABC proved to be good decision-making parameters in the diagnosis of TB and MDR-TB. The effective implementation of algorithms will depend on the conditions at each location.

Usefulness of the polymerase chain reaction dot-blot assay, used with Ziehl-Neelsen staining, for the rapid and convenient diagnosis of pulmonary tuberculosis in human immunodeficiency virus-seropositive and -seronegative individuals.

There are scarce data regarding the value of molecular tests, when used in parallel with classical tools, for the diagnosis of tuberculosis (TB) under field conditions, especially in regions with a high burden of TB-human immunodeficiency virus (HIV) co-infection. We evaluated the usefulness of the polymerase chain reaction dot-blot assay (PCR) used in parallel with Ziehl-Neelsen staining (ZN) for pulmonary tuberculosis (PTB) diagnosis, in a TB-HIV reference hospital. All sputum samples from 277 patients were tested by ZN, culture, and PCR. Performances were assessed individually, in parallel, for HIV status, history of anti-TB treatment, and in different simulated TB prevalence rates. Overall, the PTB prevalence was 46% (128/277); in HIV-seropositive (HIV(+)) individuals, PTB prevalence was 54% (40/74); the ZN technique had a lower sensitivity (SE) in the HIV(+) group than in the HIV-seronegative (HIV(-)) group (43% vs. 68%; Fisher test, P<0.05); and the SE of PCR was not affected by HIV status (Fisher test; P=0.46). ZN, in parallel with PCR, presented the following results: i) among all PTB suspects, SE of 90%, specificity (SP) of 84%, likelihood ratio (LR)(+) of 5.65 and LR(-) of 0.12; ii) in HIV(-) subjects: SE of 92%, LR(-) of 0.10; iii) in not previously treated cases: SE of 90%, LR(-) of 0.11; iv) in TB, prevalence rates of 5-20%; negative predictive values (NPV) of 98-99%. ZN used in parallel with PCR showed an improvement in SE, LR(-), and NPV, and may offer a novel approach in ruling out PTB cases, especially in not previously treated HIV(-) individuals, attended in hospitals in developing nations.

Avaliação do atendimento laboratorial a sintomáticos respiratórios para tuberculose que procuraram serviços de saúde em Canoas, Rio Grande do Sul, Brasil, 2012 / Evaluation of laboratory care provided to patients with respiratory symptoms of tuberculosis seeking public health services in Canoas, Rio Grande do Sul, Brazil, 2012 / Evaluación del atendimiento laboratorial en sintomáticos respiratorios para tuberculosis que buscaron servicios de salud en Canoas, Rio Grande del Sul, Brasil, 2012

OBJETIVO: descrever o tempo decorrido entre a identificação do sintomático respiratório para tuberculose e a liberação do resultado laboratorial, bem como entre a obtenção do resultado e o início do tratamento. MÉTODOS: estudo descritivo, com dados de casos suspeitos de tuberculose atendidos em serviços públicos de saúde no município de Canoas-RS, Brasil, em 2012. RESULTADOS: foram examinados 1.138 pacientes, com positividade de 7,47%; as medianas de tempo (i) entre identificação do paciente e entrada da amostra de escarro no laboratório e de (ii) processamento do exame foram de 2 (intervalo interquartílico [IIQ] 1-3) e 3 dias (IIQ 1-4), respectivamente, para pacientes com resultado negativo; para pacientes com resultado positivo, esses tempos foram de 2 (IIQ 1-3) e 2,5 dias (IIQ 1-4); entre a liberação do resultado e início do tratamento, transcorreram 3 dias (IIQ 0-5). CONCLUSÃO: os tempos avaliados foram considerados longos em comparação ao preconizado pelo Ministério da Saúde.

OBJECTIVE: to describe the time interval between identification of patients with respiratory symptoms of tuberculosis and laboratory test results release, and between lab results release and commencement of treatment. METHODS: this was a descriptive study with data on patients suspected of having tuberculosis who attended public health services in Canoas-RS, Brazil, in 2012. RESULTS: tests were performed in 1138 patients and positivity rate was 7.47%; medians between (i) patient identification and the sample entering the lab and (ii) processing time were 2 days (Interquartile Range [IQR] 1-3) and 3 days (IQR 1-4), respectively, for people with negative result; for patients who tested positive, these times were 2 days (IQR 1-3) and 2.5 days (IQR 1-4), and the time between release of test results and commencement of treatment was 3 days (IQR 0-5). CONCLUSION: time intervals were considered long when compared to those recommended by the Ministry of Health.

OBJETIVO: describir el tiempo transcurrido entre la identificación de un sintomático respiratorio para tuberculosis y la liberación del resultado laboratorial, y entre la obtención del mismo y el inicio del tratamiento. MÉTODOS: estudio descriptivo que incluyó datos de pacientes con sospecha de tuberculosis que consultaron servicios públicos de salud en el municipio de Canoas-RS, Brasil, en 2012. RESULTADOS: fueron examinados 1138 pacientes, siendo positivos 7,47%; las mediana de tiempo (i) entre la identificación del paciente y entrada de la muestra al laboratorio y (ii) el procesamiento fueron 2 (intervalo interquartílico [IIQ] 1-3) y 3 días (IIQ 1-4), respectivamente, para pacientes con resultado negativo; para pacientes con resultado positivo, los tiempos fueron 2 (IIQ 1-3) y 2.5 (IIQ 1-4) días y el tiempo entre liberación del resultado e inicio del tratamiento fue 3 días (IIQ 0-5). CONCLUSIÓN: los tiempos evaluados fueron considerados largos, comparados con los recomendados por el Ministerio de Salud.