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Abstract Background Tuberculosis (TB) is the leading cause of mortality among infectious diseases worldwide. Ninty five percent of TB cases and 98% of deaths due to TB occur in developing countries. Globally, the mortality rate has declined with the introduction of effective anti TB chemotherapy. Nevertheless, some patients with active TB still die while on treatment for their disease. In Ethiopia, little is known on survival and risk factors for mortality among a cohort of TB patients. The objective of the study is to determine the magnitude and identify risk factors associated with time to death among TB patients treated under DOTS programme in Addis Ababa, Ethiopia. Methods This is a retrospective cohort study. Data was obtained by assessing medical records of TB patients registered from June 2004 to July 2009 G.C and treated under the DOTS strategy in three randomly selected health centers. A step-wise multivariable Cox's regression model and Kaplan- Meier curves were used to model the outcome of interest. Mortality was used as an outcome measure. Person-years of observation (PYO) were calculated from the date of starting anti-TB treatment to date of outcome and was calculated as the number of deaths/100 PYO. Statistical analysis SPSS version 16 was used for data analysis and results were reported significant whenever P-value was less than 5%. Results From a total of 6,450 registered TB patients 236(3.7%) were died. More than 75% death occurred within eight month of treatment initiation. The mean and median times of survival starting from the date of treatment initiation were 7.2 and 7.9 months, respectively. Comparison of survival curves using Kaplan Meier curves method with log-rank test showed that the survival status was significantly different between patient categories as well as across treatment centers (P < 0.05). The death rate of pulmonary positive, pulmonary negative and extra pulmonary TB patients were 2.7%, 3.6%, and 4.3%, respectively. Body weight at initiation of anti-TB treatment ( Conclusions Most of the patients were died at the end of treatment period. This underlines the need for devising a mechanism of standardizing the existing DOTS programme and nutritional support for underweight patients for better clinical and treatment outcome.

Abstract Background There is little information concerning community-based prevalence of latent tuberculosis infection (LTBI) using T-cell based interferon-γ (IFN-γ) release assays (IGRAs), particularly in TB endemic settings. In this study, the prevalence of LTBI in the Afar pastoral community was assessed using QuantiFERON-TB Gold In-Tube (QFTGIT) and tuberculin skin tests (TST). Methods A community-based cross-sectional survey of LTBI involving 652 apparently healthy adult pastoralists was undertaken in the pastoral community of Amibara District of the Afar Region between April and June 2010. Results The prevalence of LTBI was estimated as 63.7% (363/570) using QFTGIT at the cut-off point recommended by the manufacturer (≥ 0.35 IU/ml IFN-γ), while it was 74.9% (427/570) using a cut-off point ≥ 0.1 IU/ml IFN-γ. The QFTGIT-based prevalence of LTBI was not significantly associated with the gender or age of the study participants. However, the prevalence of LTBI was 31.2% (183/587) using TST at a cut-off point ≥ 10 mm of skin indurations, and it was higher in males than females (36.8% vs. 23.5%, X2 = 11.76; p < 0.001). There was poor agreement between the results of the tests (k = 0.098, 95% CI, 0.08 - 0.13). However, there was a positive trend between QFTGIT and TST positivity (X2 = 96.76, P < 0.001). Furthermore, individuals with skin indurations ≥ 10 mm were 13.6 times more likely to have positive results using QFTGIT than individuals with skin indurations of 0 mm (adjusted OR = 13.6; 95%CI, 7.5 to 24.7, p < 0.001). Conclusions There is currently no agreed gold standard for diagnosis of LTBI. However, the higher prevalence of LTBI detected using QFTGIT rather than TST suggests that QFTGIT could be used for epidemiological studies concerning LTBI at the community level, even in a population unreactive to TST. Further studies of adults and children will be required to assess the effects of factors such as malnutrition, non-tuberculosis mycobacterial infections, HIV and parasitic infections on the performance of QFTGIT.

Abstract Background Currently, T-cell based gamma interferon (IFNγ) release assays (IGRAs) are acknowledged as the best methods available for the screening of latent tuberculosis infection (LTBI) and also as aid for the diagnosis of active tuberculosis (TB). To our information, the performance of these diagnostic tests has not been evaluated in Ethiopia. Therefore, the intent of this study was to evaluate the performance of QuantiFERON-TB Gold In-Tube (QFTGIT) in patients clinically suspected of active pulmonary TB (PTB) as well as in healthy subjects prior to its utilization for the epidemiological study of active TB and LTBI in Afar pastoralists. Methods The sensitivity of QFTGIT was evaluated in 140 subjects who were clinically suspected of PTB using the cut-off value recommended by the manufacturer (≥ 0.35 IU/ml) and disease-specific cut-off value. Sputum culture result was used as a gold standard. The specificity of the test was evaluated both in patients and in 55 tuberculin skin test (TST) negative healthy subjects. Results Out of the 140 study participants, 37 (26.4%) were positive for active PTB by culture. Out of the 37 subjects who had positive results by culture, 6 individuals were HIV-seropositive. Out of the 103 subjects who were negative by culture, 6 subjects had indeterminate results and 21 were HIV-seropositive. The performance of the test was assessed using data from 107 (31 culture positive and 76 culture negative) individuals who were clinically suspected of PTB and HIV-seronegatives. Using the manufacturer recommended cut-off value, the sensitivity of the test was 64.5% (20/31), while its specificity was 36.8% (28/76). The sensitivity of the test was increased to 77.4%, while the specificity was reduced to 23.7% using a cut-off value ≥ 0.1 IU/ml of IFNγ as disease-specific cut-off value. In TST negative healthy subjects, the specificity of the test was 58.2%. Conclusion Our findings revealed a low sensitivity of QFTGIT in the diagnosis of Mycobacterium tuberculosis (Mtb) infection in the present study area using the cut-off value recommended by the manufacturer. Nevertheless, the sensitivity increased from 64.5% to 77.4% by lowering the cut-off value recommended by the manufacturer to ≥ 0.1 IU/ml of IFNγ level. Hence, it is of practical importance to evaluate the performance of QFTGIT in population under different settings prior to its application either for the diagnosis of active TB or LTBI.

Background: Tuberculosis (TB) causes significant morbidity and mortality in refugee populations. Although Ethiopia is the third largest refugee-hosting country in Africa, there is limited published data on the prevalence and associated factors of TB in refugees. The objective of this study was to estimate the prevalence of bacteriologically confirmed pulmonary TB (PTB) and explore associated factors in presumptive TB refugees residing in refugee camps in Ethiopia., Methods: A facility-based cross-sectional study was conducted between February and August 2021 in refugee camps in Ethiopia. Data were collected consecutively from 610 presumptive TB refugees who attended for TB diagnosis in selected refugee camp clinics in Ethiopia. A pre-tested questionnaire was used to collect data, and sputum samples were collected from eligible study participants. The Xpert Mycobacterium tuberculosis (MTB)/Rifampicin (RIF) assay was performed on direct spot sputum samples, whereas morning sputum samples were processed and inoculated for bacteriological culture using Mycobacterium Growth Indicator Tube (MGIT) and Lowsteen Jensen (LJ) methods. The statistical software package (STATA version 14) was used for statistical analysis. A logistic regression model was used for the evaluation of the association between bacteriologically confirmed TB cases and the associated factors. Descriptive statistics were used for the expression of the results, and statistical significance was assumed at p < 0.05., Results: Out of 610 study participants, more than half were female (54.9%), and the mean age was 37.9 years (SD, 16.64). The prevalence of bacteriologically confirmed PTB cases among refugees residing in refugee camps in Ethiopia was 13.3% (95% CI, 10.7-16.2%) using the Xpert MTB/RIF assay and/or culture. MTB was detected in 12.8% (95% CI, 10.2-15.7%) of the individuals using the Xpert MTB/RIF assay, while culture positivity was observed in 11.6% (95% CI, 9.2-14.5%). The multivariable logistic regression model showed South Sudan origins (adjusted odds ratio, AOR = 7.74; 95% CI, 3.05-19.64), age group, 19-38 years old (AOR = 5.66; 95% CI, 1.86-17.28), and male sex (AOR = 2.69; 95% CI, 1.58-4.56) were significantly associated with the bacteriologically confirmed TB among refugees residing in refugee camps in Ethiopia., Conclusion: The prevalence of bacteriologically confirmed PTB among presumptive TB refugees residing in refugee camps in Ethiopia was high. The national TB program should strengthen TB prevention and control activities in the refugee camps of Ethiopia. Moreover, an active TB survey program should be implemented in refugee camps in Ethiopia., (© 2023. The Author(s).)

Background: Tuberculosis is a devastating and a deadly disease despite the novel advances in its diagnostic tools and drug therapy. Drug resistant Mycobacterium contributes a great share to tuberculosis mortality. Status of drug resistance and patients' awareness toward the disease is unknown in northeastern Ethiopia. Thus, the aim of this study was to determine the phenotypic and genotypic drug sensitivity patterns and associated factors in Oromia Special Zone and Dessie Town, northeastern Ethiopia., Methods: In a cross-sectional study, 384 smear positive tuberculosis cases were recruited and Löwenstein-Jensen culture was done. The performance of GenoTypic MTBDRplus assay using the conventional BACTEC MGIT 960 as a "gold standard" was determined. Drug resistant strains were identified using spoligotyping. Pearson Chi-square test was used to determine the association of drug sensitivity test and tuberculosis type, lineages, dominant strains and clustering of the isolates., Results: The 384 smear positive Mycobacterium samples were cultured on LJ media of which 29.2% (112/384) as culture positive. A fair agreement was found between MTBDRplus assay and the conventional MGIT test in detecting the Mycobacterium tuberculosis with sensitivity, specificity, positive and negative predictive value of 94.2, 30.2, 68.4 and 76.5%, respectively. Among LJ culture positive samples 95 of them gave valid result for MTBDRplus assay and 16.8% (16/95) as drug resistant. Similarly, MGIT subculture was made for the 112 isolates and 69 of them gave positive result with 15.9% (11/69) as drug resistant. Cohen's kappa value showed almost a perfect agreement between the two testing methods in detecting rifampicin (sensitivity 100% and specificity 98.3%) and multi-drug resistance (sensitivity 83.3% and specificity 100%). Spoligotyping identified 76.5% (13/17) of the drug resistant isolates as Euro-American and family 33 as the predominant family. Significant association was observed between drug resistant isolates and the dominant strains (χ2: 34.861; p = 0.040) of the Mycobacterium., Conclusion: Higher magnitude of drug resistance was found in the study area. The GenoTypic MDRTBplus assay had an acceptable drug sensitivity testing performance.

Background: Tuberculosis (TB) is caused by Mycobacterium tuberculosis complex (MTBC). Mapping the genetic diversity of MTBC in high TB burden country like Ethiopia is important to understand principles of the disease transmission and to strengthen the regional TB control program. The aim of this study was to investigate the genetic diversity of Mycobacterium tuberculosis complex (MTBC) isolates circulating in the South Omo, southern Ethiopia., Methods: MTBC isolates (N = 156) were genetically analyzed using spacer oligotyping (spoligotyping) and mycobacterial interspersed repetitive unit-variable number of tandem repeat (MIRU-VNTR) typing. Major lineages and lineages were identified using MTBC databases. Logistic regression was used to correlate patient characteristics with strain clustering., Results: The study identified Euro-American (EA), East-African-Indian (EAI), Indo-Oceanic (IO), Lineage&#95;7/Aethiops vertus, Mycobacterium bovis and Mycobacterium africanum major lineages in proportions of 67.3% (105/156), 22.4% (35/156), 6.4% (10/156), 1.9% (3/156), 1.3% (2/156) and 0.6% (1/156), respectively. Lineages identified were Delhi/CAS 23.9% (37/155), Ethiopia&#95;2 20.6% (32/155), Haarlem 14.2% (22/155), URAL 14.2%(22/155), Ethiopia&#95;3 8.4% (13/155), TUR 6.5% (10/155), Lineage&#95;7/Aethiops vertus 1.9% (3/155), Bovis 1.3% (2/155), LAM 1.3% (2/155), EAI 0.6% (1/155), X 0.6% (1/155) and Ethiopia H 37 Rv-like strain 0.6% (1/155). Of the genotyped isolates 5.8% (9/155) remained unassigned. The recent transmission index (RTI) was 3.9%. Orphan strains compared to shared types (AOR: 0.09, 95% CI: 0.04-0.25) were associated with reduced odds of clustering. The dominant TB lineage in pastoral areas was EAI and in non-pastoral areas was EA., Conclusion: The epidemiological data, highly diverse MTBC strains and a low RTI in South Omo, provide information contributing to the TB Control Program of the country.

Background: Drug resistant tuberculosis (TB) has become a persistent health threat in Ethiopia. In this respect, baseline data are scarce in many parts of high TB burden regions including the different zones of Ethiopia., Methods: A total of 111 culture positive M. tuberculosis isolates were recovered from TB patients and identified using region of difference (RD) 9 based polymerase chain reaction (PCR) and spoligotyping. Thereafter, their drug sensitivities to Rifampicin (RIF) and Isoniazid (INH) were evaluated using GenoType MTBDRplus assay., Results: The result showed that 18.0% (20/111) of the isolates were resistant to either RIF or INH. Furthermore, 16.7 and 23.8% of the isolates from new and retreatment cases were resistant to any of the two anti-TB drugs, respectively. Multi-drug resistant (MDR) TB was detected on 1.8% (2/111) of all cases. Significantly higher frequencies of any drug resistance were observed among Euro-American (EA) major lineage (χ 2 : 9.67; p = 0.046)., Conclusion: Considerably high proportion of drug resistant M. tuberculosis strains was detected which could suggest a need for an increased effort to strengthen TB control program in the study area.

Background: Female genital tuberculosis (FGTB) is known to cause severe tubal disease leading to infertility and its incidence closely parallels with the overall prevalence of tuberculosis (TB) in a community. Its magnitude is underreported because diagnosis is difficult and requires invasive techniques. In this study we determined the prevalence of endometrial tuberculosis and characterized isolates among women who underwent endometrial biopsy for evaluation of various conditions at a Tikur Anbessa Specialized Hospital (TAHS), Addis Ababa, Ethiopia., Methods: A cross sectional study was conducted on 152 consecutive gynecologic patients who underwent endometrial biopsy for different gynecologic diseases. Endometrial tissue taken for routine histopathology examination was shared after informed consent was obtained from the patient and subjected to polymerase chain reaction (PCR) and culture for Mycobacterium tuberculosis (Mtb)., Results: The prevalence of endometrial TB in this study by IS1081PCR was 4.6% (7/152) while culture proven endometrial TB was 2.6% (4/152). However, histological examination identified only 2/152 (1.3%) endometrial tuberculosis. While all culture proven TB samples were also PCR positive for Mtb, only one histologic proven endometrial TB was culture and PCR positive. All of the four isolates by culture were M. tuberculosis., Conclusion: This study has shown that the magnitude of endometrial TB is fairly high in gynecologic patients visiting outpatient departments for various complaints and PCR detects more cases than culture or Histopathology.

Background: Understanding the types of strains and lineages of Mycobacterium tuberculosis (M. tuberculosis) circulating in a country is of paramount importance for tuberculosis (TB) control program of that country. The main aim of this study was to review and compile the results of studies conducted on strains and lineages of M. tuberculosis in Ethiopia., Methods: A systematic search and review of articles published on M. tuberculosis strains and lineages in Ethiopia were made. PubMed and Google Scholar databases were considered for the search while the keywords used were M. tuberculosis, molecular epidemiology, molecular typing spoligotyping and Ethiopia., Result: Twenty-one studies were considered in this review and a total of 3071 M. tuberculosis isolates and 3067 strains were included. These studies used spoligotyping and identified five lineages including Indo-Ocean, East Asian/Beijing, East African-Indian, Euro-American and Ethiopian in a proportion of 7.1%, 0.2%, 23.0%, 64.8%, and 4.1%, respectively. Thus, Euro-American was the most frequently (64.8%) occurring Lineage while East Asian was the least (0.2%) frequently occurring Lineage in the country. Surprisingly, the Ethiopian Lineage seemed to be localized to northeastern Ethiopia. In addition, the top five clades identified by this review were T, CAS, H, Manu and Ethiopian comprising of 48.0%, 23.0%, 11.0%, 6.0% and 4.1% of the strains, respectively. Furthermore, predominant shared types (spoligotype patterns) identified were SIT149, SIT53, SIT25, SIT37, and SIT21, each consisting of 420, 343, 266, 162 and 102 isolates, respectively, while, on the other hand, 15% of the strains were orphan., Conclusion: According to the summary of the results of this review, diversified strains and lineages of M. tuberculosis were found in Ethiopia, and the frequencies of occurrence of these strains and lineages were variable in different regions of the country. This systematic review is registered in the PRISMA with the registration number of 42017059263.

Background: Identification of the types of strains of Mycobacterium tuberculosis (M. tuberculosis) complex causing tuberculosis (TB) could contribute to TB control program of specific geographic region as well as it could add knowledge onto the existing literature on TB worldwide. The objective of the present study was to identify the species and strains of M. tuberculosis complex causing pulmonary tuberculosis in central Ethiopia., Methods: A health institution- based cross-sectional study was conducted on 338 smear positive TB cases visiting three hospitals between October 2012 and September 2013. Morning and spot sputum samples were collected before the starting of treatment regimens. Thus, a total of 338 pooled sputum samples collected from these cases. Samples were cultured on Löwenstein Jensen media and the isolates were identified by the region of difference (RD) 9 based polymerase chain reaction (PCR) and spoligotyping., Result: Of the total isolates 98.6% of the isolates were identified to be M. tuberculosis while the remaining 1.4% were identified as M. africanum. Further, typing of M. tuberculosis using spoligotyping lead to the identification of 90 different strains of M. tuberculosis. Of these strains, 32 were clustered consisting of more than one isolate while the remaining 58 strains were unique consisting of single isolate. Thus, 79.3% (223/281) of the isolates were found in the clustered while only 20.6% (58/281) of the strains were unique. Forty-five of the spolgotyping patterns were registeredin the SITVIT2 or SpolDB4 database in while the remaining 45 were notfound in the database and hence were orphan strains. The dominant strains were SIT53, SIT149, and SIT54, consisting of 43, 37 and 34 isolates, respectively. Classification of the spoligotype patterns using TB-insight RUN TB-Lineage showed that 86.8, 6.4, 5, 1.4% ofthe isolatesbelonged to the Euro-American lineage, East-African-Indian, Indo-oceanic and M. africanum, respectively., Conclusion: The identification of clustered and new strains using spolygotyping in present study does not give conclusive finding as spoligotyping has low discriminatory power. Thus, further identification of these isolates using mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VENTR) and or whole genome sequencing (WGS) recommended.

Background: Tuberculous lymphadenitis (TBLN) diagnosis has been a true challenge solely by clinical evidence in developing countries, due to limited the diagnostic facility on hand. However, the availability and affordability of available diagnostic tools in resource-limited settings like Ethiopia necessitates the quest for other techniques with added value over direct Z-N microscopy. Therefore, we aimed at to assess whether the concentration of lymph node aspirate similarly improves the detection rate of tuberculous lymphadenitis or not., Materials and Methods: A cross-sectional study design was conducted on 132 individual subjects presumptive for tuberculous lymphadenitis from February to October 2013 in Addis Ababa, Ethiopia. Fine needle aspirate (FNA) samples were collected from the cases and cultured on Löwenstein-Jensen (LJ) slants. Identification of species and strains of mycobacteria was made by region of difference (RD) based polymerase chain reaction (PCR). Data entry and statistical analyses were performed by SPSS version 20. The confidence level of 95% was used for statistical significance., Result: A total of 132 study subjects were included in our study. Of these 56.1% (74/132) were positive for M. tuberculosis on culture. The detection rate of direct smear microscopy and the concentration method were 29.5 and 65.2% respectively. The sensitivity of direct smear microscopy was 43.2%, for concentrated smear microscopy 94.5%, for PCR 93.2% and for cytomorphology 95.4%. The level of agreement of concentrated ZN smear microscopy was 0.62 which was very similar with kappa of 0.58 of molecular (PCR) technique. AFB positivity by the concentration method and molecular method was increased in caseous aspirates as compared to purulent and hemorrhagic aspirates though it was not statistically significant (p-value = 0.18) and (p = 0.62) respectively., Conclusion: The concentration of FNA (Fine Needle Aspirate) aspirates for acid-fast smear microscopy similarly improves the sensitivity of acid fast bacilli in diagnosing of TBLN.

Background: Ethiopia, a high tuberculosis (TB) burden country, reports one of the highest incidence rates of extra-pulmonary TB dominated by cervical lymphadenitis (TBLN). Infection with Mycobacterium bovis has previously been excluded as the main reason for the high rate of extrapulmonary TB in Ethiopia., Methods: Here we examined demographic and clinical characteristics of 953 pulmonary (PTB) and 1198 TBLN patients visiting 11 health facilities in distinct geographic areas of Ethiopia. Clinical characteristics were also correlated with genotypes of the causative agent, Mycobacterium tuberculosis., Results: No major patient or bacterial strain factor could be identified as being responsible for the high rate of TBLN, and there was no association with HIV infection. However, analysis of the demographic data of involved patients showed that having regular and direct contact with live animals was more associated with TBLN than with PTB, although no M. bovis was isolated from patients with TBLN. Among PTB patients, those infected with Lineage 4 reported "contact with other TB patient" more often than patients infected with Lineage 3 did (OR = 1.6, CI 95% 1.0-2.7; p = 0.064). High fever, in contrast to low and moderate fever, was significantly associated with Lineage 4 (OR = 2.3; p = 0.024). On the other hand, TBLN cases infected with Lineage 4 tended to get milder symptoms overall for the constitutional symptoms than those infected with Lineage 3., Conclusions: The study suggests a complex role for multiple interacting factors in the epidemiology of extrapulmonary TB in Ethiopia, including factors that can only be derived from population-based studies, which may prove to be significant for TB control in Ethiopia.

Background: Tuberculosis (TB) is the leading cause of mortality among infectious diseases worldwide. Ninty five percent of TB cases and 98% of deaths due to TB occur in developing countries. Globally, the mortality rate has declined with the introduction of effective anti TB chemotherapy. Nevertheless, some patients with active TB still die while on treatment for their disease. In Ethiopia, little is known on survival and risk factors for mortality among a cohort of TB patients. The objective of the study is to determine the magnitude and identify risk factors associated with time to death among TB patients treated under DOTS programme in Addis Ababa, Ethiopia., Methods: This is a retrospective cohort study. Data was obtained by assessing medical records of TB patients registered from June 2004 to July 2009 G.C and treated under the DOTS strategy in three randomly selected health centers. A step-wise multivariable Cox's regression model and Kaplan- Meier curves were used to model the outcome of interest. Mortality was used as an outcome measure. Person-years of observation (PYO) were calculated from the date of starting anti-TB treatment to date of outcome and was calculated as the number of deaths/100 PYO. Statistical analysis SPSS version 16 was used for data analysis and results were reported significant whenever P-value was less than 5%., Results: From a total of 6,450 registered TB patients 236(3.7%) were died. More than 75% death occurred within eight month of treatment initiation. The mean and median times of survival starting from the date of treatment initiation were 7.2 and 7.9 months, respectively. Comparison of survival curves using Kaplan Meier curves method with log-rank test showed that the survival status was significantly different between patient categories as well as across treatment centers (P < 0.05). The death rate of pulmonary positive, pulmonary negative and extra pulmonary TB patients were 2.7%, 3.6%, and 4.3%, respectively. Body weight at initiation of anti-TB treatment (<35 kg), patient category, year of enrollment and treatment center were independent predictors for time to death., Conclusions: Most of the patients were died at the end of treatment period. This underlines the need for devising a mechanism of standardizing the existing DOTS programme and nutritional support for underweight patients for better clinical and treatment outcome.

Background: There is little information concerning community-based prevalence of latent tuberculosis infection (LTBI) using T-cell based interferon-γ (IFN-γ) release assays (IGRAs), particularly in TB endemic settings. In this study, the prevalence of LTBI in the Afar pastoral community was assessed using QuantiFERON-TB Gold In-Tube (QFTGIT) and tuberculin skin tests (TST)., Methods: A community-based cross-sectional survey of LTBI involving 652 apparently healthy adult pastoralists was undertaken in the pastoral community of Amibara District of the Afar Region between April and June 2010., Results: The prevalence of LTBI was estimated as 63.7% (363/570) using QFTGIT at the cut-off point recommended by the manufacturer (≥0.35 IU/ml IFN-γ), while it was 74.9% (427/570) using a cut-off point≥0.1 IU/ml IFN-γ. The QFTGIT-based prevalence of LTBI was not significantly associated with the gender or age of the study participants. However, the prevalence of LTBI was 31.2% (183/587) using TST at a cut-off point≥10 mm of skin indurations, and it was higher in males than females (36.8% vs. 23.5%, X2=11.76; p<0.001). There was poor agreement between the results of the tests (k=0.098, 95% CI, 0.08-0.13). However, there was a positive trend between QFTGIT and TST positivity (X2=96.76, P<0.001). Furthermore, individuals with skin indurations≥10 mm were 13.6 times more likely to have positive results using QFTGIT than individuals with skin indurations of 0 mm (adjusted OR=13.6; 95%CI, 7.5 to 24.7, p<0.001)., Conclusions: There is currently no agreed gold standard for diagnosis of LTBI. However, the higher prevalence of LTBI detected using QFTGIT rather than TST suggests that QFTGIT could be used for epidemiological studies concerning LTBI at the community level, even in a population unreactive to TST. Further studies of adults and children will be required to assess the effects of factors such as malnutrition, non-tuberculosis mycobacterial infections, HIV and parasitic infections on the performance of QFTGIT.

Background: Currently, T-cell based gamma interferon (IFNγ) release assays (IGRAs) are acknowledged as the best methods available for the screening of latent tuberculosis infection (LTBI) and also as aid for the diagnosis of active tuberculosis (TB). To our information, the performance of these diagnostic tests has not been evaluated in Ethiopia. Therefore, the intent of this study was to evaluate the performance of QuantiFERON-TB Gold In-Tube (QFTGIT) in patients clinically suspected of active pulmonary TB (PTB) as well as in healthy subjects prior to its utilization for the epidemiological study of active TB and LTBI in Afar pastoralists., Methods: The sensitivity of QFTGIT was evaluated in 140 subjects who were clinically suspected of PTB using the cut-off value recommended by the manufacturer (≥ 0.35 IU/ml) and disease-specific cut-off value. Sputum culture result was used as a gold standard. The specificity of the test was evaluated both in patients and in 55 tuberculin skin test (TST) negative healthy subjects., Results: Out of the 140 study participants, 37 (26.4%) were positive for active PTB by culture. Out of the 37 subjects who had positive results by culture, 6 individuals were HIV-seropositive. Out of the 103 subjects who were negative by culture, 6 subjects had indeterminate results and 21 were HIV-seropositive. The performance of the test was assessed using data from 107 (31 culture positive and 76 culture negative) individuals who were clinically suspected of PTB and HIV-seronegatives. Using the manufacturer recommended cut-off value, the sensitivity of the test was 64.5% (20/31), while its specificity was 36.8% (28/76). The sensitivity of the test was increased to 77.4%, while the specificity was reduced to 23.7% using a cut-off value ≥ 0.1 IU/ml of IFNγ as disease-specific cut-off value. In TST negative healthy subjects, the specificity of the test was 58.2%., Conclusion: Our findings revealed a low sensitivity of QFTGIT in the diagnosis of Mycobacterium tuberculosis (Mtb) infection in the present study area using the cut-off value recommended by the manufacturer. Nevertheless, the sensitivity increased from 64.5% to 77.4% by lowering the cut-off value recommended by the manufacturer to ≥ 0.1 IU/ml of IFNγ level. Hence, it is of practical importance to evaluate the performance of QFTGIT in population under different settings prior to its application either for the diagnosis of active TB or LTBI.