|Year : 2020 | Volume
| Issue : 1 | Page : 39-47
Epidemiological profile and surveillance activity of tuberculosis in South Batinah, Oman, 2017 and 2018
Zayid K Al Mayahi1, Ibtisam AlAufi2, Badriya Al Ghufaili3, Zawan Al Balushi4, Zakiya Al Mughazwi5, Emad Mohammed4, Rahmdil Essa5, Haga M Yousif3, Adhraa K Al Mayahi6, Azza Al Hattali1, Fakhriyah Al Ghafri Al Ghafri1, Nasser Al Shaqsi1, Khalid Salim2, Hamid A Elmutashi17, Fatma AI Yaquobi1
1 Directorate General for Health Services in South Batinah Governorate, MOH, Al-Rustaq, Oman
2 Rustaq Regional Hospital, Al-Rustaq, Oman
3 Rustaq Extended Health Center, Al-Rustaq, Oman
4 Barka Extended Health Center, Al-Rustaq, Oman
5 Musanaah Extended Health Center, Al-Rustaq, Oman
6 College of Arts and Social Sciences, Sultan Qaboos University, Muscat, Oman
7 General Directorate for Disease Surveillance and Control, MOH, Muscat, Oman
|Date of Submission||02-Dec-2019|
|Date of Decision||20-Dec-2019|
|Date of Acceptance||31-Dec-2019|
|Date of Web Publication||6-Mar-2020|
Zayid K Al Mayahi
P.O. Box: 543, PC 329, Rustaq, South Batinah
Source of Support: None, Conflict of Interest: None
Background: Understanding the current surveillance activity and the challenges is important to ensure a continuous success toward the elimination goal for tuberculosis (TB). South Batinah Governorate (SBG) ranked the fourth on the top reporting governorates in the period 2010–2016 in Oman. The objective of this study is to describe the epidemiological profile and activities of the surveillance program of TB in the SBG in the years 2017 and 2018. Methods: A retrospective quantitative analysis and a qualitative review were performed to the surveillance data present in the department of disease surveillance and control in the SBG in the years 2017 and 2018. Results: A total of 39 pulmonary TB (PTB) and 21 extrapulmonary TB (EPTB) cases were diagnosed in 2017 and 2018. More Omanis (22, 56.4%) were diagnosed with PTB compared to non-Omanis; however, the EPTB was solely diagnosed among Omanis (P < 0.001). Majority of the TB patients (35%) were between 30 and 49 years. More than 50% of the TB cases of both the types were diagnosed in <3 months, and the median of diagnosis delay was 33.5 (standard deviation = 95.5). Bacillus Calmette–Guérin vaccine scar was present in only 20.5% of the PTB patients, compared to 57.1% of EPTB (P = 0.004). Patients with PTB presented mainly with cough (31, 79.5%), loss of weight and appetite (25, 64.1%), and fever (22, 56.4%). Enlarged lymph nodes and loss of weight and appetite were the common symptoms among EPTB patients, 38.1 for each (P < 0.001). Staffing, incomplete notifications, difficulty in tracing the results, and absence of regular feedbacks are the major existing challenges. Conclusion: SBG continues to sustain low incidence rate of tuberculosis; however, additional strategies are urgently required for further reduction. Hence, the priority is to enhance all essential components of the surveillance system at this stage.
Keywords: Extrapulmonary tuberculosis, Oman, pulmonary tuberculosis, surveillance, tuberculosis
|How to cite this article:|
Al Mayahi ZK, AlAufi I, Al Ghufaili B, Al Balushi Z, Al Mughazwi Z, Mohammed E, Essa R, Yousif HM, Al Mayahi AK, Hattali AA, Ghafri FA, Shaqsi NA, Salim K, Elmutashi1 HA, Yaquobi FA. Epidemiological profile and surveillance activity of tuberculosis in South Batinah, Oman, 2017 and 2018. Int J Mycobacteriol 2020;9:39-47
|How to cite this URL:|
Al Mayahi ZK, AlAufi I, Al Ghufaili B, Al Balushi Z, Al Mughazwi Z, Mohammed E, Essa R, Yousif HM, Al Mayahi AK, Hattali AA, Ghafri FA, Shaqsi NA, Salim K, Elmutashi1 HA, Yaquobi FA. Epidemiological profile and surveillance activity of tuberculosis in South Batinah, Oman, 2017 and 2018. Int J Mycobacteriol [serial online] 2020 [cited 2020 Apr 10];9:39-47. Available from: http://www.ijmyco.org/text.asp?2020/9/1/39/280145
| Introduction|| |
Tuberculosis (TB) still remains one of the most challenging public health threats in the world, particularly in middle- and low-income countries. The latest figures of the World Health Organization (WHO) show a huge burden of the disease globally. About 1.3 million deaths were caused by TB among HIV-negative patients in 2017, in addition to 300,000 deaths among HIV-positive patients. In the same way, the multidrug-resistant mycobacterium is on the rise, while there is a big struggle finding new effective drugs with less toxicity and resistance. However, controlling transmission of resistant strains would ultimately require searching for new drugs, regimens, new diagnostic approaches along with working to improve the social support, and living standards generally.
Before 1970, Oman had a tough time with scarce resources, poor infrastructure, and endemicity of many infectious diseases. However, the following decades were characterized with a rapid development on different aspects of Oman's modern life. Subsequently, in a reasonably short time, it has been regarded as a country with low incidences for many diseases and with a successful elimination of a number of diseases too. Administratively, Oman is divided into 11 governorates and inhabited with almost 4,601,706 people (census 2018).
TB incidence rates in the whole Oman had declined dramatically from 91 to 7.8 per 100,000 in the period 1981–2016, with the highest average decline rate of 9%/year noticed in the first 10 years. The years 2010–2016 were similarly characterized by a continuous reduction in the overall reported TB incidence rate. During this period, South Batinah Governorate (SBG) ranked the fourth on the top reporting governorates of TB cases following Muscat, North Batinah, and Dhofar.
At present, Oman is considered a low incident country of TB with a rate of <10 cases/100,000. This outstanding stage of TB control was achieved through important and solid action framework since the 1970s. The National TB Program (NTP) was established in 1975 and became integrated within the department of communicable disease in the Ministry of Health (MOH) in 1990. The implementations of different strategies recommended by the WHO were other important assets to expedite the control of TB including the Directly Observed Therapy, Short-Course in 1995, the Stop TB Strategy in 2006, and the End TB Strategy in 2014.
This study aims to describe the epidemiological profile of TB in the SBG in the years 2017 and 2018 and the activities related to the surveillance program.
| Methods|| |
SBG has a 425,707 population size representing the 5th most populated governorate in Oman (census 2018). Geographically, it is located in the northern side, on the shores of the Gulf of Oman, bordered by governorates of Muscat to the East, Dakhiliyah to the South, and Dhahera and North Batinah to the West. It includes six provinces called wilayats: Barka, Musanaah, Rustaq, Nakhal, Wadi Al Mawel, and Awabi [Figure 1].
The main regional governmental services including medical services are centered in Rustaq wilayat. Likewise, the general directorate of health services of SBG is based in Rustaq together with the main reference secondary hospital. There are a total of 21 primary health facilities distributed in the six wilayats, including three main polyclinics in Rustaq, Barka, and Musanaa which provide specialty services as well. Moreover, two medical fitness examination centers are located in Barka and Rustaq, which provide examination and testing services for non-Omanis coming for work purposes.
Study design and data collection
A retrospective quantitative analysis was performed on the public health surveillance of TB program for the years 2017 and 2018 in the SBG. Also, a qualitative review was performed to describe the tuberculosis surveillance activities in the same period. TB cases were classified based on the WHO case definitions., In case where a patient was asymptomatic or the information was missing, the date of symptom onset was assumed to be the same day of diagnosis.
The data collected were organized, tabulated, and statistically analyzed using EpiInfo (version 7; Centers for Disease Control and Prevention, Atlanta, Georgia, USA). The numerical data were presented in terms of mean and standard deviation (SD) and the categorical data were presented as number and percentage. The Chi-square was used to test for differences in subcategories. The P value adopted was P < 0.05.
Permission to conduct this analysis was obtained from disease surveillance and control directorate in SBG. This evaluation and analysis were done as a nonresearch program. All data collected through record reviews were anonymized.
| Results|| |
[Table 1] shows the characteristics of TB patients. A total number of 60 cases of TB were reported from SBG in the years 2017 and 2018, of which 39 (65%) were pulmonary TB (PTB) and 21 (35%) were extrapulmonary TB (EPTB). There were more males diagnosed with TB compared to females for both PTB and EPTB (21 [53.9%] and 13 [60%], respectively). More Omanis (22, 56.4%) were diagnosed with PTB compared to non-Omanis; however, the EPTB was solely diagnosed among Omanis (P < 0.001). Majority of the TB patients (35%) were between 30 and 49 years; however, there was only one EPTB case diagnosed under 10 years of age. The two most common comorbidities among both the types of TB were diabetes and hypertension. For PTB, 38.5% had diabetes, followed by hypertension (15.4%), compared to 19.1% diabetic and 14.3% hypertensive among EPTB cases. More than 50% of the TB cases of both the types were diagnosed in <3 months, and the median of diagnosis delay was 33.5 (SD = 95.5). However, about 52.4% of the EPTB cases took more than 3 months to get diagnosed, compared to 20.5% of PTB. While majority (45%) of the TB patients were unemployed, housemaids accounted for 20.5% among PTB patients, and there was only one health-care worker who had EPTB. Bacillus Calmette–Guérin (BCG) vaccine scar was present in only 20.5% of the PTB patients, compared to 57.1% of EPTB, while the status of the scar was not identified in at least a quarter of each type (P = 0.004). However, in relation to the nationality, the vaccination rate was higher among Omanis compared to non-Omanis (18 [42%] and 2 [12%], respectively). Patients with PTB presented mainly with the following symptoms: cough (31, 79.5%), loss of weight and appetite (25, 64.1%), and fever (22, 56.4%). On the other hand, enlarged lymph nodes and loss of weight and appetite were the common symptoms among EPTB patients, 38.1% for each (P < 0.001). Majority of the TB cases were from Barka 26 (43.3%), followed by Rustaq (15, 25%), Musanaa (15, 25%), and Wadi Al Mawel (4, 6.7%). Mapping of the cases is demonstrated in [Figure 2]. Eight cases were from both Bangladesh and India, followed by three Filipinos and two Tanzanians. Only one case was diagnosed form the following nationalities: Ethiopian, Nigerian, Ugandan, and Chinese. Almost 70% of the non-Omani patients were diagnosed in the medical fitness examination centers in Rustaq and Barka during their routine checkup, whereas the remaining 30% of the cases sought medical evaluation mainly from the private sector.
|Figure 2: Distribution of tuberculosis cases in the six wilayats in South Batinah Governorate|
Click here to view
[Table 2] demonstrates the investigations used for the diagnosis of TB. GeneXpert test was done for 22 (56.4%) of the PTB cases, of which mycobacterium TB was detected in the majority (19, 86.4%). None of the cases had rifampicin resistance, while two cases were unknown. Furthermore, 7 out of 11 of EPTB patients who had GeneXpert test turned positive, and only one case showed rifampicin resistance.
The tuberculin skin test (TST) was done for 14 (35.9%) patients of PTB, of which majority 12 (30.8%) were positive, whereas 13 out of 14 EPTB patients had positive TST. As for radiograph investigations, the chest X-ray showed suggestive signs of TB for all PTB patients who underwent X-ray. On the other hand, only 6 patients had Xray suggestive of infection out of 16 EPTB patients, while for the remaining 5 patients, chest Xray was not done (P < 0.001).
[Table 3] demonstrates the diagnostic approach for tuberculosis cases. Only one case was diagnosed based on clinical judgment, compared to 38 (97.4%) bacteriologically confirmed cases. Nearly 75% were positive on sputum smear. Specimens used for the diagnosis were mainly sputum (36, 92.3%); however, there was only one induced sputum sample and two bronchoalveolar lavage samples. The EPTB cases were mainly diagnosed through lymph node samples (9, 42.9%) and pleural samples (3, 14.3%), while information for six patients were missing.
Sensitivity rates of antituberculosis medications are displayed in [Table 4]. The percentage of sensitivity was as follows: 100% ethambutol, 98% rifampicin and streptomycin, 96% isoniazid, and 87.5% pyrazinamide. There were 8 (16%) cases with monoresistance compared to only one case with dual resistance to isoniazid and rifampicin. The fatality rate among 60 TB patients was 10%; however, patients may have died secondary to other comorbid conditions. The total number of registered contacts was 409, of which 332 (80%) were older than 5 years. The estimated percentage of latent TB among contacts older than 5 years was about 26%.
The TB program in the SBG is run by a team consisting of a public health specialist from the regional public health authority (disease surveillance and control), a treating physician and an assistant nurse in the regional hospital, and three focal nurses in the primary health care. The public health specialist is expected to handle many responsibilities such as ensuring monthly sputum examinations, contact screening, treatment adherence to MOH manual, completeness and updating of records, training the focal nurses and health-care workers, reducing defaulters of screening and treatment, studying and analyzing the TB cases, and ensuring the quality, timeliness, and completeness of reporting case and monthly report by the health-care provider in the region. However, in reality, he also manages other important communicable diseases, along with administrative responsibilities which obviously affect the quality of work of TB program.
The regional focal point receives the notifications of confirmed TB cases by fax from the secondary hospital in the region or from other hospitals outside the region. Every new notification of a confirmed case is given a unique index number, filed, and all related updates (cultures result, clinical updates, contacts screening) received subsequently are entered through a data entry software (Epidata version 3.1, Odense, Denmark,) which generates an excel file. A copy of the excel file is also shared with the NTP in the MOH.
Screening of contacts is done by three focal trained nurses in the three wilayats (Barka, Musanaa, and Rustaq). A copy of each TB notification is also faxed to the focal nurse where the patient belongs. The nurse calls the patient's contacts and gives them appointment to come to the polyclinic to be counseled and screened. Screening starts by thorough evaluation of any symptoms or signs and assessing how close they were to the patient. Investigations include TST or QuantiFERON test and chest X-ray. However, if a patient is symptomatic, the erythrocyte sedimentation rate, complete blood count, and three acid-fast bacilli samples will also be done along with GeneXpert and culture. The latent TB is diagnosed based on TST reading of 10 millimetres (mm) or more, or a positive QuantiFERON test, provided that active pulmonary TB is ruled out. If TST is found negative on the first presentation, a patient's contact is retested after 3 months. For the children <5 years of age, the treatment is started immediately for contacts of PTB cases. The contact visits are recorded on a TB register in the three focal wilayats. The data are then transcribed into the electronic excel database of latent TB with the regional epidemiologist. The weekly clinical progress of TB patients (PTB or EPTB) is also added continuously to the file by the TB focal nurse in the admitting hospital. A copy of the file is also shared with the NTP.
The main observations throughout the years 2017 and 2018 were as following: (a) the regional focal point and the three focal nurses in the polyclinics were not fully dedicated for the TB activity in the region, but they were also responsible about many other important works; (b) inadequate handover and training to the newly appointed focal health staff; (c) incompleteness of a significant number of notifications and the difficulty to trace results and updates from other stakeholders; (d) lack of standardization of the TB contact register and screening protocols in the three polyclinics in SBG; (e) no regular feedbacks were provided to the health-care workers working in the primary health system; (f) no reports or feedbacks were shared with the decision-makers in the region; (g) many health-care workers working either in private or governmental health institutes were neither aware that TB disease is free of charge, nor about the legal implication for not referring or treating TB patients; and (h) the unregulated increase in the volume of patients in the primary care affected the detection capability of many general practitioners.
| Discussion|| |
The total incidence rate of TB in SBG during the 2 years 2017 and 2018 is estimated as 8.6 and 5.6/100,000 population, respectively, whereas the total incidence rate for the whole Oman in 2018 was 5.9 as reported in the WHO website. However, in the context of potential gaps in the surveillance system, there is a high possibility of a significant unreported number of cases as well. The underreporting of cases was also suggested by a previous study conducted in one of the tertiary hospitals in Oman where PTB, EPTB, and disseminated TB comprised 53%, 37%, and 10%, respectively.
Overcoming challenges encountered in the surveillance system would certainly lead to the detection of further cases and simultaneously cease the chain of transmission. Undoubtedly, the priority is to ensure the adequacy of staffing dedicated for TB program, increase the awareness and training for all health-care workers, especially the general practitioners, and develop a timely reporting electronic surveillance system rather than relying on the conventional ways of updating and communicating. The sensitivity and vigilance of the surveillance system is also hard to evaluate in the absence of the notification system for the presumptive TB cases in the whole Oman, a global recommendation by the WHO.
The non-Omanis diagnosed with PTB constitute a big proportion nearly 45% in SBG. Many of them sought medical advice significantly late after their condition has deteriorated. Late medical consultation among the expatriates is possibly attributed to the negative reaction against the Omani regulations which compel non-Omani PTB patients working in high-risk occupations to be repatriated home after completing the initial treatment and evaluation. In addition to the fact that many are unaware about the free costs for the evaluation and management of presumptive TB cases and that many of them have low income. In general, the migrants to the low TB incidence countries, as the case of Oman, are the ongoing reservoir of new TB infections, especially those coming from south and southeast countries., It is also suggested that the activation of latent TB among the expatriates in the GCC countries takes place within the first 2 years after arrival; thus, seriously considering the screening of latent TB seems essential to successfully reaching the preelimination stage of TB by 2035., Slightly more cases were diagnosed among the males compared to females, same as in many published works. Apparently, TB has occurred in all age categories, particularly among 30–49 years for both the types of TB and over 70 years for EPTB. Elderly people are generally more vulnerable to develop TB infections possibly due to the decline in the physiological and metabolic functions, alveolar macrophage ability, and comorbidities as well. Diagnosis delay is another significant challenge where the risk of infection transmission in the community increases. The estimated median of delay for both PTB and EPTB is 1 and 2 months, respectively. While majority of the patients on both PTB and EPTB are diagnosed in <3 months, a significant proportion of patients get even longer than 3 months. A survey in Tunisia, for instance, found a diagnosis delay median of about 52.56 days from onset of symptoms to therapy initiation, while London surveillance analysis 1998–2000 had a median diagnosis delay of 49 days., The data also show that BCG scar is absent for a large proportion of people, especially among the PTB, whereas the status for at least a quarter of the cases was unknown. Until present, there is no known vaccine able to prevent the disease in the adults; however, the BCG given at birth has shown the prevention of severe forms of TB in the children. The common symptoms for PTB found in this retrospective analysis were cough, loss of weight/appetite, and fever, which match the known classical presentations. Majority of the EPTB patients were diagnosed through lymph nodes samples, which also goes in accordance with other studies., There was a better utilization of GeneXpert test in 2018 compared to the previous year. The WHO recommends the use of Xpert MTB/RIF in preference to other conventional methods for both PTB and EPTB. The TST was used more frequently for the diagnosis of EPTB. However, a previous study found differences in the clinical presentation of TB patients based on the TST result; the disseminated disease (military or the combined of PTB and EPTB) was more likely associated with negative TST. Apparently, the chest X-ray played an essential role for the diagnosis of PTB cases, in comparison to EPTB. In general, the chest radiography is the mainstay of diagnosis of parenchymal diseases in the primary PTB, whereas the computed tomography (CT) is more sensitive to the detection of lymphadenopathy and also the characterization of parenchymal disease. The CT is also the best which evaluates the abdominal lymphadenopathy in EPTB; however, tuberculous spondylitis, as well as central nervous system TB, are best evaluated by magnetic resonance imaging., Resistance ratio goes in accordance with a previous finding of a study performed in a tertiary hospital in Oman, where pyrazinamide had the highest resistance compared to zero resistance of ethambutol, while varying resistance degrees were found for the rest of drugs. However, the TB mortality reported here is less than the rate found in a previous study (15%), 31 deaths out of 205 cases, where the advanced age, low body weight, negative sputum TB smear, pulmonary involvement, human immunodeficiency virus infection, and noncitizen status were found as the main risk factors for TB-related mortality.
Noticeably, SBG achieved high rate of contacts tracing and screening. The estimated percentage of latent TB among contacts (older than 5 years) was apparently affected by a number of limitations. For instance, a significant proportion of contacts were not compliant with the screening, while other contacts did screening in other governorates and their results were not available. Also, the electronic excel file designed for the contacts tracing was limited to 25 contacts for every notified TB case. The reading of Mantoux test was sometimes unreliable, especially when the trained focal nurse or doctor was not available. Besides, there was a discrepancy of data between the registers in the polyclinics and the electronic database. However, a previous study found the incidence of latent TB among healthcare workers in a tertiary hospital in Oman as 33.2%, while another metaanalysis study concluded that the prevalence in the highincome countries is 28.1%.,
| Conclusion|| |
SBG continues to sustain low incidence rate of tuberculosis; however, additional strategies are urgently required for further reduction. Hence, the priority is to enhance all essential components of the surveillance system at this stage, including early detection and treatment of cases, prompt screening for the contacts and ensuring of high-quality and validated data. Developing an intelligent electronic surveillance system and establishing presumptive notification form are also required at this stage. Further studies are required to understand the risk factors and perception level among the Omani population about TB, while screening of latent TB should also be considered among people coming from high prevalent TB countries. However, all of these would be impossible to achieve without securing the adequate number of highly qualified and trained staff for TB program.
This analysis was limited by the small number of cases and the incompleteness of the data for many patients.
We are in debt to Mrs. Khalsa Al Dhuhli and Mrs. Ruqayyah Al Shihi for their appreciated efforts and support. Authors also acknowledge the cooperation and support of our colleagues from all health institutions in the SBG.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Jena L, Harinath BC. Anti-tuberculosis therapy: Urgency for new drugs and integrative approach. Biomed Biotechnol Res J 2018;2:16-9. [Full text]
Kumar A, Singh AK, Upadhyay V, Pandey J. Epidemiology of multi-drug-resistant tuberculosis in Northern India. Biomed Biotechnol Res J 2018;2:112-21. [Full text]
Al Awaidy ST. Tuberculosis elimination in Oman: Winning the war on the disease. ERJ Open Res 2018;4. pii: 00121-2018.
Matteelli A, Rendon A, Tiberi S, Al-Abri S, Voniatis C, Carvalho AC, et al
. Tuberculosis elimination: Where are we now? Eur Respir Rev 2018;27. pii: 180035.
National Tuberculosis Control Programme, Department of Communicable Disease Surveillance and Control, Directorate General of Health Affairs. 4th
ed. Manual of TB Control Programme; 2007. p. 56.
Gaifer Z. Epidemiology of extrapulmonary and disseminated tuberculosis in a tertiary care center in Oman. Int J Mycobacteriol 2017;6:162-6.
] [Full text]
Heuvelings CC, de Vries SG, Grobusch MP. Tackling TB in low-incidence countries: Improving diagnosis and management in vulnerable populations. Int J Infect Dis 2017;56:77-80.
Heuvelings CC, de Vries SG, Greve PF, Visser BJ, Bélard S, Janssen S, et al
. Effectiveness of interventions aiming at identifying and managing tuberculosis among hard-to-reach populations: A systematic review. Lancet Infect Dis 2017;56:77-80.
Rendon A, Centis R, Zellweger JP, Solovic I, Torres-Duque CA, Robalo Cordeiro C, et al
. Migration, TB control and elimination: Whom to screen and treat. Pulmonology 2018;24:99-105.
Ahmad S, Mokaddas E, Al-Mutairi NM. Prevalence of tuberculosis and multidrug resistant tuberculosis in the Middle East region. Expert Rev Anti Infect Ther 2018;16:709-21.
Piergallini TJ, Turner J. Tuberculosis in the elderly: Why inflammation matters. Exp Gerontol 2018;105:32-9.
Ben Amar J, Hassairi M, Ben Salah N, Charfi R, Tritar F, Fourati R, et al
. Pulmonary tuberculosis: Diagnostic delay in Tunisia. Med Mal Infect 2016;46:79-86.
Rodger A, Jaffar S, Paynter S, Hayward A, Carless J, Maguire H. Delay in the diagnosis of pulmonary tuberculosis, London, 1998-2000: Analysis of surveillance data. BMJ 2003;326:909-10.9
Lyon SM, Rossman MD. Pulmonary tuberculosis. Microbiol Spectrum 2017;5:TNMI7-0032-2016. doi:10.1128 /microbiolspec.TNMI7-0032-2016.
Forssbohm M, Zwahlen M, Loddenkemper R, Rieder HL. Demographic characteristics of patients with extrapulmonary tuberculosis in Germany. Eur Respir J 2008;31:99-105.
Xpert MTB/RIF Implementation Manual: Technical and Operational HowTo; Practical Considerations. Annex 2, Standard Operating Procedure (SOP) for processing extrapulmonary specimens (CSF, lymph nodes and other tissues) for Xpert MTB/RIF assay. Geneva: World Health Organization; 2014. Available from: https://www.ncbi. nlm.nih.gov/books/NBK254320/
. [Last accessed on 2019 Dec 02].
Auld SC, Click ES, Heilig CM, Miramontes R, Cain KP, Bisson GP, et al
. Association between tuberculin skin test result and clinical presentation of tuberculosis disease. BMC Infect Dis 2013;13:460.
Im JG, Itoh H, Shim YS, Lee JH, Ahn J, Han MC, et al
. Pulmonary tuberculosis: CT findings-early active disease and sequential change with antituberculous therapy. Radiology 1993;186:653-60.
Hoffman EB, Crosier JH, Cremin BJ. Imaging in children with spinal tuberculosis. A comparison of radiography, computed tomography and magnetic resonance imaging. J Bone Joint Surg Br 1993;75:233-9.9.
Trivedi R, Saksena S, Gupta RK. Magnetic resonance imaging in central nervous system tuberculosis. Indian J Radiol Imaging 2009;19:256-65.
] [Full text]
Gaifer Z, Babiker A, Rizavi D. Epidemiology of drug-resistant tuberculosis in a tertiary care center in Oman, 2006-2015. Oman Med J 2017;32:36-40.
Gaifer ZA. Risk factors for tuberculosis mortality in a tertiary care center in Oman, 2006-2016. Int J Mycobacteriol 2017;6:356-9.
] [Full text]
Khamis F, Al-Lawati A, Al-Zakwani I, Al-Abri S, Al-Naamani J, Al-Harthi H, et al
. Latent tuberculosis in health care workers exposed to active tuberculosis in a tertiary care hospital in Oman. Oman Med J 2016;31:298-303.
Fox GJ, Barry SE, Britton WJ, Marks GB. Contact investigation for tuberculosis: A systematic review and meta-analysis. Eur Respir J 2013;41:140-56.
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]