The Journal of Association of Chest Physicians

: 2014  |  Volume : 2  |  Issue : 1  |  Page : 25--31

Active case finding of sputum positive pulmonary tuberculosis in household contacts of tuberculosis patients in Karachi, Pakistan

Tahir Rizwan Khan1, Zeeshan Ahmed1, Mubashir Zafar1, Nighat Nisar1, Shahina Qayyum2, Khalid Shafi3,  
1 Department of Community Medicine, Dow International Medical College, Ojha Institute of Chest Diseases, Karachi, Pakistan
2 Department of Community Medicine, Ojha Research and Monitoring Cell, Ojha Institute of Chest Diseases, Karachi, Pakistan
3 Department of Community Medicine, Dow Medical College, Dow University of Health Sciences, Karachi, Pakistan

Correspondence Address:
Mubashir Zafar
Department of Community Medicine, Dow International Medical College, Dow University of Health and Sciences Gulzar-e-Hijri, KDA Scheme-33, Suparco Road, Mahkma-e-Mosmiat, Karachi


Background: Pakistan holds rank 8 th among the world countries in which high prevalence of tuberculosis (TB) is present. There is evidenced that up to 30% of close contacts of TB patients become infected and at least half of them progress to active disease. The aim of this study was to screen active contacts of sputum positive pulmonary TB (SS +ve PTB) among household contacts (HHCs) of TB patients in Karachi, Pakistan. Materials and Methods: Cross-sectional study, which was conducted at chest clinics of Karachi. Total 750 HHCs were screened out of which 135 diagnosed smear positive TB patients was registered as index cases (ICs) from July 2012 till March 2013. Logistic regression analysis was carried out to estimate the odds ratio (OR) of different associated factors. Results: Prevalence among males (6.1%) compared with female (5.6%). The crude OR for age less than 15 years was 0.28 (95% confidence interval (CI) 0.14-0.55). Eighty-eight HHCs (11.73%) were found to have SS +ve TB. Disease frequency was significantly higher in HHCs who were smokers (adjusted OR 36.41; 95% CI 12.07, 109.79), had age less than 12 years (adjusted OR 3.63; 95% CI 1.68, 7.86), and who lived in houses less than 80 square yards (adjusted OR 3.77; 95% CI 1.27, 6.05). Conclusion: The IC with positive sputum smear constitutes great risk for TB infection and disease in HHC. There is needed for contact tracing strategy in the high-risk population.

How to cite this article:
Khan TR, Ahmed Z, Zafar M, Nisar N, Qayyum S, Shafi K. Active case finding of sputum positive pulmonary tuberculosis in household contacts of tuberculosis patients in Karachi, Pakistan.J Assoc Chest Physicians 2014;2:25-31

How to cite this URL:
Khan TR, Ahmed Z, Zafar M, Nisar N, Qayyum S, Shafi K. Active case finding of sputum positive pulmonary tuberculosis in household contacts of tuberculosis patients in Karachi, Pakistan. J Assoc Chest Physicians [serial online] 2014 [cited 2022 May 28 ];2:25-31
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Full Text


In the era of modern medicine, tuberculosis (TB) still poses a great threat to human health. The disease caused by Mycobacterium tuberculosis (MTB), is often deadly in nature. Though, TB can affect any organ system, [1],[2] pulmonary TB (PTB) has the greatest impact on public health. TB had practically been declared a global emergency by World Health Organization (WHO) almost 2 decades ago with 1.4 million deaths in the year 2010 alone. [3] Despite the presence of effective anti-TB therapy and overall good treatment outcomes, case detection rates for TB has been poor due to ineffective case finding techniques. It is a well-established fact that PTB is most infectious when MTB are present in the sputum. Many studies [4],[5],[6],[7] have reported this finding. Family and household contacts (HHCs) top them all in whom TB is found to be most frequent. [8],[9] Close contact screening is therefore standard practice in developed countries. [10],[11] Such screening programs intend to find active cases of TB in high-risk populations. Several studies [12],[13],[14],[15],[16],[17] have proven that active case finding among HHCs yields substantially more TB cases than passive case detection.

According to the WHO report on estimated burden of TB in 2010, Pakistan stands at 8 th number worldwide. [16] In 1999 total estimated new cases of TB were 269,000 equivalent to 177 per 100,000 inhabitants and only 8% of the total cases had access to directly observed treatment, short-course (DOTS). [16] Annually more than 50,000 deaths were associated with TB in Pakistan. [16] After 10 years, in 2009, the situation has gotten worse. The total estimated new cases (with or without HIV) have risen to 420,000 equivalents to 231 per 100,000 with case detection rate of 63%; prevalence of 373 per 100,000 and mortality of 68,000. [16]

In Pakistan, there are very few studies on active case finding of TB among HHCs and prevalence of the disease among them. Most of which are restricted to smaller settings. There is a certain need that active case finding method among HHCs to be evaluated in our setting for the detection of TB cases on a larger scale. This study was investigating the burden of sputum positive TB (SS +ve TB) among the HHCs of TB patients in Karachi.

 Materials and Methods

Operational definition

TB infection: Tuberculin skin test (TST) >10 mm induration in non-HIV infected and >5 mm in HIV infected children. [18]

Bacteriological confirmed TB: The presence of at least one sample smear positive for acid-fast bacilli or culture positive for MTB in combination with TB symptoms (persistent cough >2 weeks, unexplained weight loss, poor weight gain, or lethargy) or positive chest radiograph. [19]

Probable TB: Chest X-ray finding indicative of active TB in conjunction with TB symptoms.

Presumptive TB: Refers to a patient who presents with symptoms or signs suggestive of TB (previously known as a TB suspect).

Index case (IC): The first TB case identified in the household, TB patient registered for DOTS in Iqbal Yad, Malir, or Nazimabad Chest Clinic.

Household: A group of people living within one residence who share meals together and identified a head of family who made decisions for the household. [20]

HHC: A HHC was defined as an individual who had resided in the household for at least 7 consecutive days during the 3 months before to the diagnosis of TB in the IC. [20]

Case detection: Means that TB is diagnosed in a patient and is reported within the national surveillance system. [21]

Case detection rate: "The number of new smear positive cases notified divided by the number of new smear positive cases estimated for that year, expressed as a percentage." [22]

Active case finding

A screening process in which household and other close contacts of infectious cases are identified and tested for TB infection and active disease. [12]

Descriptive cross-sectional study was done. Study was conducted in public sector hospitals Ojha Institute of Chest Diseases (OICD), Dow University of Health Sciences. The population of interest consisted of HHCs of smear positive TB patients residing in Karachi. Since these HHCs, living in the same house with SS +ve TB patients, are at high risk for contracting the infection and active disease themselves. This study was a high risk screening. The study's main outcome variable was the presence or absence of smear positive PTB and independent variables for study were age, gender, education, Bacile Clamette Geurin (BCG) vaccination, family size, household income, house size, smoking, and relation with IC. Human immunodeficiency virus (HIV) testing was not done due to low prevalence in the community. Sample size was calculated by using Open Epi software. [23] Keeping the frequency of identified HHCs having TB at evaluation in developing countries as 4.5%, [24] confidence level at 95%, and population size of 450 (average number of SS +ve TB patients registering for DOTS during 3 months); the sample size came out to be 131, maximum error of ±3% with estimate. Total HHC included in the study was 135 respondent. Consecutive sampling technique was used. [20] Inclusion criteria for study those.

New smear positive TB casesResident of KarachiRegister at OICD.

Exclusion criteria for study those

Who refuse to participate in the studyTB patients who were diagnosed as having any form of drug resistant TB (DRTB).

Data were collected from July 2012 till March 2013, 150 consecutive cases of smear positive PTB patients were screened at OICD. Of these 150 cases, 135 were enrolled as ICs into the study. Patients who were not enrolled either refused to participate in the study (n = 6) or all of their HHCs could not be screened either due to nonavailability or social reasons (n = 9). These 15 patients were removed from the analyses.

Phase I: A total of 135 ICs were recruited, a primary principal investigator have done interview using predesigned questionnaire to gather basic information regarding exact address, age, education, total number of people living in the house, size of the house, household income, and smoking habit.

Phase II: Based on the primary interview of the ICs, primary visit at their homes was carried out and TB having cough identified suspects for at least 1 week (productive or otherwise).

Phase III: TB suspects among HHCs, who needed supplementary laboratory Investigations, were brought to OICD or were given travel money at 100 Pakistan rupees (PKR) per suspect to bring them to OICD for sputum screening. Suspects, having productive cough, were asked to give three sputum samples collected on spot-morning-spot basis for sputum smear acid-fact bacilli (AFB) microscopy. Hiring, training on questionnaire, and screening techniques of two medical officers (one male and one female). Identification of ICs registered at three filter clinics was done after informed consent. Questionnaire-based interviews were done by the principle investigator (PI) of the ICs for basic information including the number and specifics of their HHCs. Primary visits were done by the PI and data collectors to evaluate and fill the questionnaire for every HHC to obtain requiring information. Contacts with symptoms consistent with the signs and symptoms of TB were brought to OICD for screening. All suspects were screened at OICD.

Statistical analysis

Data was initially entered and cleaned using Microsoft Excel version 2007. Statistical package for social sciences (SPSS) version 16 was used for the analysis. Cleaning and coding of the data was done before analysis. Complete case analysis method was used and cases with missing data were removed from the final analysis.

Descriptive analysis was done for all independent variables. Mean ± standard deviation was calculated for continuous variables like age and household income was calculated and median value was calculated for the family size.

Inferential statistics were calculated using binary logistic regression to estimate the effect of age, gender, education, family size, house size, household income, BCG vaccination, smoking status, and relationship with IC on the presence or absence of disease. Variables with P ≤ 0.05 or those of biological or social importance were selected for multiple logistic regression analysis to calculate adjusted odds ratio (OR). Ethics committee of Dow University of Health Sciences approved the study. The committee approved the consent procedure. The written consent was taken from each participant. Assent forms were provided for minors. Assent and consent from minors was given by caretaker or guardians. Consent form attached with each questionnaire. Ethics committee approved consent procedure.


A total of 1,500 household were found and out of 750 HHCs were screened from 135 ICs. Out of these 750 contacts, 160 were found to be symptomatic having productive cough for at least 1 week. Forty-six HHCs had cough for at least 1 week, while the rest had it for 2 or more weeks [Table 1] and [Table 2], [Figure 1].{Figure 1}{Table 1}{Table 2}

Sociodemographic characteristics

Sociodemographic characteristics of HHCs are shown in [Table 2].

Frequency of TB among household contacts

Of all 750 HHCs, 165 were symptomatic. Among the symptomatic, smear positive TB was found in 88 HHCs. Hence, smear positive TB was present in 11.7% of HHCs [Table 3].{Table 3}

Inferential statistics

Inferential statistics were calculated in two steps. Initially, univariate analyses were run. Variables with P value less than 0.05 were put to multivariable analysis.

Univariate analysis: [Table 4] shows univariate analysis was for variables associated with TB among HHCs. Predictor variables included all sociodemographic characteristics of HHCs. Binary logistic regression was done for this purpose. [Table 3] shows comparison of groups of HHCs with and without TB by different variables. Of nine variables understudy, five were found to be associated with TB among HHCs. Age less than 12 years was negatively associated with TB among HHCs with crude OR 0.28 and 95% confidence interval (CI) 0.14, 0.55 (P < 0.01). House size less than equal to 80 square yards was positively linked to the presence of TB in HHCs with crude OR 3.95 (95% CI 2.15, 7.26; P value 0.00). Whereas household income less than equal to 15,000 PKR per month was also positively associated with the disease (crude OR 2.52; 95% CI 1.60, 3.97; P < 0.01). Similarly, being smoker and being spouse of IC was also found out to be positively associated with the TB among HHCs with crude OR 33.78 (95% CI 12.17, 93.79; P < 0.01), and 2.35 (95% CI 1.15, 4.78; P value 0.19), respectively.{Table 4}

Multivariable analysis

[Table 5] shows multivariable analysis for variables associated with TB among HHCs. Variables associated with smear positive TB in univariate analysis were retained for multivariable analysis. After adjustment, three out of five variables from univariate analyses were found to be significantly affecting smear positive TB among HHCs. Age less than 15 years was found protective of smear positive TB with adjusted OR 0.26 and 95% CI 0.13, 0.56. Whereas house size less than or equal to 80 square yards was found to positively associated with the disease (OR 3.08; 95% CI 1.40, 6.74). Smoking among HHCs was most significantly associated with smear positive TB with OR 33.83 (95% CI 11.59, 98.77).{Table 5}


This study attempted to address the issue of screening people for the disease who share the same household with the TB patients registered at the largest TB center in the country. We found out 160 TB suspects on clinical and physical signs and symptoms. Out of these 160 TB suspects, 88 (55%) had SS +ve TB. The prevalence of sputum positivity in HHCs was 11.7%. This is in accordance with another local study conducted at Abbasi Shaheed Hospital Karachi where 12.7% of the HHCs were found to have active PTB. [25]

In comparison with other high burden countries of the region like India and China (these two countries combined, have 35% of global TB burden), Pakistan has much higher prevalence of SS +ve PTB among HHCs. A study from China [21] has found frequency of HHCs suffering from SS +ve PTB reaching as high as 6.89%. Similarly in India, [26] a study pointed out that the prevalence of SS +ve PTB among HHCs is around 4.3%. The reason for these are yet to be explored since our study simply focused on finding the prevalence of HHCs having SS +ve TB.

There are many factors associated with high TB prevalence and spread in third world countries. Poverty, overcrowding, and lack of basic health facilities to treat the disease are few of the many factors. Our study took into account the basic factors and looked for their association with TB frequency among HHCs of TB patients. When these factors were taken individually (in univariate analyses), we found out that low income, that is, less than 15,000 PKR (crude OR 6.14; 95% CI 2.17, 17.41); smoking (crude OR 33.78; 95% CI 12.17, 93.79); smaller house size, that is less than 80 square yards (crude OR 2.77; 95% CI 1.05, 7.72); and close relationship with IC, that is, being spouse of IC (crude OR 1.69; 95% CI 0.70, 4.08) were associated with the presence of TB among HHCs which is in accordance with the international data. Whereas, age less than 12 years was negatively associated with TB among HHCs with crude OR 0.12 (95% CI 0.041, 0.35) which is in contrast with the findings of few researchers. [20],[27] As showed by Borgdorff et al., [27] young source cases of PTB generates young secondary cases. One reason for this contradictory finding might be due to methodology, as we applied the same diagnostic criteria for all age groups, that is, screening the HHCs via sputum AFB staining due to scarcity of resources. Children under 5 years are especially difficult to diagnose through this technique since they are less compliant to sputum AFB screening. Since the symptoms may be subtle and relying only on AFB microscopy is not ideal for diagnosing the disease. [28],[29],[30] This might have resulted in underestimation of the disease frequency in younger age group. Second explanation can be as stated in the National Guidelines for Diagnosis and Management of Tuberculosis in Children that the children under 12 are rarely infectious, that means, they very rarely suffer from smear positive TB. Therefore, in our study, we did not find a single case of smear positive TB under age 12.

In the final model only three factors were found to be significantly related to the presence of SS +ve TB among HHCs. House size less than 80 square yards (adjusted OR 2.77; 95% CI 1.27, 6.05) and smoking among contacts (adjusted OR 36.41; 95% CI 12.07, 109.79). While age less than 12 years was found to be protective in association from "smear positive TB" with adjusted OR 3.63 with 95% CI 1.68, 7.86. This is in accordance with the global literature. Paucibacillary TB in children as a reason why no cases were found in children less than 12 years of age. [31]


There were several of limitations in this study. The study only considered SS +ve TB patients as they are the most infectious and the single most important source of transmitting the disease, it relied on the sputum AFB for the diagnosis. Hence, sputum negative PTB patients would have been missed. Children under 12 years, on the other hand, are considered noninfectious since their pulmonary lesions are small and non-cavitary. Only symptomatic individuals were tested for TB. Only symptomatic (>1/52 cough) individuals were tested for TB. There is therefore a possibility that more HHCs (asymptomatic) could have had TB but were not tested.

Strengths of the study

This study had based its findings on data collected from three main TB clinics of Karachi. These clinics, being a part of public sector health facility, entertains majority of the city's population. It is estimated that 50-70% of cases in Karachi were seen in these clinics, remaining cases were treated in private health facilities and few cases was that include in this study. Thus we can say that our study sample was representative of the population of interest.


There is very high prevalence of SS +ve TB among HHCs of TB patients being 11.7%. Greater age (more than 15 years, smaller house size (less than 80 square yards), and smoking are identified as factors associated with presence of TB among HHCs.


Following recommendations are made in the light of this study:

A proper active contact tracing system should be formed in association with Pakistan TB Control Program to screen all HHCs of TB patientsAny active contact tracing system should be shown to be cost-effective operationally before implementation.


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