Tuberculosis (TB) is a chronic infectious disease and is a major public health problem [
According to different reports, the incidence of EPTB has been increasing among TB patients across Ethiopia since the 1990s and recently the estimated numbers of EPTB cases reached 32% in the country which is higher than other African countries [
Besides regional variation of WHO report [
A few cross-sectional studies were conducted among presumptive EPTB cases in Ethiopia for determination of risk factors and prevalence of EPTB which ranged from 9.9% to 29.8% [
Hospital based cross-sectional study was conducted from March 1 to June 30, 2017.
The study was conducted at Dessie Referral Hospital which is located at South Wollo, Dessie town, Amhara Region, Northeast Ethiopia. Dessie is located in the Northeastern part of Ethiopia, 401 km from the capital city, Addis Ababa. The town’s location is 11081N latitude and 390381E longitude. The hospital serves as a Referral Hospital with more than 300 beds and gives different inpatient and outpatient services to more than 7 million populations in the surrounding area and the adjacent regions.
The study population comprised all clinically presumptive EPTB cases who visited adult outpatient departments (OPD and inpatient wards of Dessie Referral Hospital during the study period). The minimum representative sample size was determined using the single population proportion formula: N = z2 p (1-p)/ d2, where N is the number of presumptive EPTB cases; Z is standard normal distribution value at 95% CI which is 1.96; P is the prevalence of EPTB = 29.8% [
Presumptive EPTB case is any person who presents with signs and symptoms of EPTB including chronic lymphadenitis and body fluid accumulations like meningitis, pleural effusion, ascites, and others with clinical suspicion of tuberculosis. The definition of EPTB case is based on Ethiopian 2013 Ministry of Health guideline, and defined as TB in organs other than the lungs proven by a bacteriologically positive specimen from an extrapulmonary site. A bacteriologically confirmed case is one from whom a biological specimen is positive by smear microscopy, culture, or WHO-approved rapid diagnostics (such as Xpert MTB/RIF).
Presumptive EPTB cases aged ≥ 18 years and volunteering to participate were considered for inclusion, but presumptive cases who were critically ill and active pulmonary and extrapulmonary tuberculosis patients who were on anti-TB treatment were excluded from the study.
Before analysis, each sample was carefully homogenized and partitioned into two parts aseptically inside a biosafety cabinet (BSC). One of the split samples with small amount was used to prepare a smear on new, clean, unscratched frosted glass slide. Smears were fixed and stained with the staining reagents, auramine O stain (0.1% auramine O solution, 0.5% acid-alcohol, and 0.3% methylene blue). After drying, stained smears were examined under the light-emitting diode (LED) fluorescent microscopy (Primo Star iLED, Carl Zeiss, Gottingen, Germany) with 200x and 400x magnification for acid fast bacilli (AFB) [
For Gene Xpert MTB/RIF assay, one of the split samples with sufficient volume was treated with sample reagent (SR) containing NaOH and isopropanol as per the manufacturer’s instruction [
Data entry and analysis were made using SPSS version 20.0 statistical software. Descriptive statistics were used for analysis of patient characteristics. Chi-square tests and logistic regression analysis were done to determine the presence of a statistically significant association between explanatory variables and the outcome variable. To identify independently associated factors, multivariate logistic regression model was employed by taking presence of EPTB as an outcome variable. All explanatory variables that were associated with the outcome variable in the bivariate analysis (P ≤ 0.2) were included in the multivariate logistic regression model. Odds Ratio (OR), p value, and their 95% Confidence Intervals (CI) were calculated and the result was considered statistically significant at P ≤ 0.05.
The Ethical Review Committee of Wollo University, College of Medicine and Health Sciences, approved the study. A permission and support letter were also obtained from the management committee of Dessie Referral Hospital. Patients signed informed consent form to participate in the study. Information obtained at any course of the study was kept confidential. Positive results were made available to clinicians for decision-making as early as available.
From a total of 353 presumptive EPTB cases who enrolled during the study period, majority (52.4%) were males. The age of the participants ranged from 18 to 77 years with mean of 38.16 years (± SD= 13.45 years) and 45.6% of study participants were in the age ranging from 31 to 50 years. About half (51.6%) of study participants were rural dwellers and 60.3% had a monthly income of less than 1500 Ethiopian birr. The majority (74.2%) of the study subjects were married and 40.0% were illiterate. About 61.2% of study participants had greater than three family members living together in the same room (Table
Sociodemographic characteristics of presumptive EPTB cases at Dessie Referral Hospital, from March 1 to June 30, 2017.
| Frequency | Percent |
---|---|---|
| ||
18-30 | 132 | 37.4 |
31-50 | 161 | 45.6 |
>50 | 60 | 17.0 |
| ||
Male | 185 | 52.4 |
Female | 168 | 47.6 |
| ||
Urban | 171 | 48.4 |
Rural | 182 | 51.6 |
| ||
Married | 262 | 74.2 |
Single | 91 | 25.8 |
| ||
House wife | 99 | 28.0 |
Merchant | 84 | 23.8 |
Farmer | 93 | 26.3 |
Others | 77 | 21.8 |
| ||
Illiterate | 143 | 40.5 |
Grades 1-8 | 93 | 26.3 |
Grade 9 & above | 117 | 33.1 |
| ||
≤1500 birr | 213 | 60.3 |
>1500 birr | 140 | 39.7 |
| ||
1-3 | 137 | 38.8 |
>3 | 216 | 61.2 |
Almost half of (49%) study participants had chronic diseases of whom 28.32% had diabetic mellitus (DM) followed by chronic kidney disease (21.96%) and hypertension (19.65%). However, lower proportion of study participants had previous history of PTB infection (9.1%) and contact with PTB patients (4.5%) and have had a habit of cigarette smoking (7.6%), alcohol drinking (14.7%), and consumption of raw milk (14.7%) (Table
Lifestyle and clinical characteristics of presumptive EPTB cases at Dessie Referral Hospital, from March 1 to June 30, 2017.
Variable | Frequency | Percent |
---|---|---|
| ||
Yes | 27 | 7.6 |
No | 326 | 92.4 |
| ||
Yes | 52 | 14.7 |
No | 301 | 85.3 |
| ||
Yes | 32 | 9.1 |
No | 321 | 90.9 |
| ||
Yes | 173 | 49.0 |
No | 180 | 51.0 |
| ||
Kidney | 38 | 21.96 |
HIV | 32 | 18.49 |
DM | 49 | 28.32 |
Hypertension | 34 | 19.65 |
Others | 20 | 11.56 |
| ||
Yes | 16 | 4.5 |
No | 337 | 95.5 |
| ||
Yes | 52 | 14.7 |
No | 301 | 85.3 |
Among all presumptive EPTB cases, the most commonly suspected site of infection was meninges (52.1%), followed by pleural cavity (30.9%) as shown in Table
Prevalence of Gene Xpert MTB/RIF assay and LED-FM confirmed EPTB patients at Dessie Referral Hospital, from March 1 to June 30, 2017.
| | | | ||||
---|---|---|---|---|---|---|---|
| | | p-value | | | p-value | |
CSF | 184(52.1) | 174 (94.6) | 10 (5.4) | | 6(3.3) | 178 (96.7) | |
Peritoneal fluid | 45(12.7) | 42(93.3) | 3(6.7) | 0(0) | 45(100) | ||
Pleural fluid | 109(30.9) | 96 (88.1) | 13(11.9) | 2(1.8) | 107 (98.2) | ||
LNA | 15(4.3) | 10 (66.7) | 5 (33.3) | 1(6.7) | 14 (93.3) | ||
| 322(91.22) | 31(8.78) | 9(2.5) | 344(97.5) |
CSF: cerebrospinal fluid; LNA: lymph node aspirate.
In the current study, sociodemographic characteristics such as age, sex, residence, monthly income, family size living together, occupation, and educational level were not significantly associated with EPTB. Furthermore, bivariate analysis also showed that lifestyle characteristics such as cigarette smoking, alcohol drinking, and consumption of raw milk were not significantly associated with EPTB. However, history of previous PTB infection (COR: 2.73; 95%CI: 1.03-7.26) and contact with PTB patients (COR: 3.83; 95%CI: 1.16-12.68) were significantly associated with EPTB Gene Xpert MTB/RIF assay positivity. On multivariate logistic regression analysis, previous history of PTB (AOR: 2.81; 95%CI: 1.05-7.54) remains the only predictor of EPTB (Table
Factors associated with Gene Xpert MTB/RIF assay positivity among presumptive EPTB cases at Dessie Referral Hospital, from March 1 to June 30, 2017.
| Freq | Xpert result | COR (95%CI) | P-value | AOR (95%CI) | p-value | |
---|---|---|---|---|---|---|---|
Negative=n (%) | Positive=n (%) | ||||||
| |||||||
18-30 | 132 | 119(90.2) | 13(9.8) | ref | |||
31-50 | 161 | 147(91.3) | 14(8.7) | 0.87(0.40-1.93) | 0.734 | ||
>50 | 60 | 56(93.3) | 4 (6.7) | 0.65(0.20-2.10) | 0.475 | ||
| |||||||
| |||||||
Male | 185 | 170(91.9) | 15(8.1) | ref | |||
Female | 168 | 152(90.5) | 16(9.5) | 1.19(0.57-2.49) | 0.639 | ||
| |||||||
| |||||||
Urban | 171 | 161(94.2) | 10(5.8) | ref | |||
Rural | 182 | 161(88.5) | 21(11.5) | 2.1(0.95-4.60) | 0.064 | 2.14(0.97-4.71) | 0.059 |
| |||||||
| |||||||
Married | 262 | 238(90.8) | 24(9.2) | ref | |||
Single | 91 | 84(92.3) | 7(7.7) | 0.83(0.34-1.99) | 0.670 | ||
| |||||||
| |||||||
House wife | 99 | 88(88.9) | 11(11.1) | ref | |||
Merchant | 84 | 79(94.0) | 5(6.0) | 0.51(0.17-1.52) | 0.225 | ||
Farmer | 93 | 83(89.2) | 10(10.8) | 0.96(0.39-2.39) | 0.937 | ||
Others | 77 | 72(93.5) | 5(6.5) | 0.56(0.19-1.67) | 0.296 | ||
| |||||||
| |||||||
Illiterate | 143 | 128(89.5) | 15(10.5) | 1.84(0.73-4.68) | 0.199 | ||
Grades 1-8 | 93 | 84(90.3) | 9(9.7) | 1.68(0.60-4.71) | 0.320 | ||
Grade 9 & above | 117 | 110(94.0) | 7(6.0) | ref | |||
| |||||||
| |||||||
<1500 birr | 213 | 191(89.7) | 22(10.3) | 1.68(0.75-3.76) | 0.209 | ||
>1500 birr | 140 | 131(93.6) | 9(6.4) | ref | |||
| |||||||
| |||||||
<4 | 137 | 125(91.2) | 12(8.8) | ref | |||
4 & above | 216 | 197(91.2) | 19(8.8) | 1.0(0.47-2.14) | 0.990 | ||
| |||||||
| |||||||
Yes | 27 | 22(81.5) | 5(18.5) | 2.6(0.92-7.50) | 0.072 | ||
No | 326 | 300(92.0) | 26(8.0) | ref | |||
| |||||||
| |||||||
Yes | 52 | 45(86.5) | 7(13.5) | 1.8(0.73-4.41) | 0.20 | ||
No | 301 | 277(92.0) | 24(8.0 | ref | |||
| |||||||
| |||||||
Yes | 32 | 26(81.2) | 6(18.8) | 2.73(1.03-7.26) | 0.044 | 2.8(1.05-7.54) | 0.040 |
No | 321 | 296(92.2) | 25(7.8) | ref | |||
| |||||||
| |||||||
Yes | 173 | 156(90.2) | 17(9.8) | 1.29(0.62-2.71) | 0.497 | ||
No | 180 | 166(92.2) | 14(7.8) | ref | |||
| |||||||
| |||||||
Yes | 16 | 12(75.0) | 4(25.0) | 3.83(1.16-12.68) | 0.028 | ||
No | 337 | 310(92.0) | 27(8.0 | ref | |||
| |||||||
| |||||||
Yes | 52 | 48(92.3) | 4(7.7) | 0.86(0.28-2.53) | 0.764 | ||
No | 301 | 274(91.0) | 27(9.0) | ref |
COR: crude odds ratio; AOD: adjusted odds ratio.
Nowadays EPTB is becoming a major concern of tuberculosis control programs. Formerly, it was more prevalent in developed nations than developing countries but these days it has high proportion in developing nations including Ethiopia [
In this study, the most common suspected extrapulmonary sites were meninges, pleural, peritoneal, and lymph nodes in decreasing order. However, TB disease detection rate was highest among patients suspected of having TB lymphadenitis (33.3%) followed by pleural effusion (11.9%) as shown in Table
In this study the overall prevalence of Gene Xpert MTB/RIF assay positive EPTB cases was 8.8% which is lower than study conducted in Gondar, Ethiopia (26.2%) [
Moreover, it could be attributed to difference in sociodemographic characteristics of study participants and variation in study design or laboratory diagnostic techniques. For instance, studies conducted in Gondar, Ethiopia, utilized culture and concentrated specimens for Gene Xpert MTB/RIF assay [
In our study, Gene Xpert MTB/RIF assay analysis also showed significant variation among nonrespiratory samples to detect Mycobacterium tuberculosis complex (p=0.001) but no statistical difference was observed using LED-FM (Table
In our analysis, Gene Xpert MTB/RIF assay and LED-FM did not provide similar results with 0.427 Cohen’s Kappa measure of agreement. However, all samples which were LED-FM smear-positive were also Gene Xpert MTB/RIF assay positive. This is due to the high sensitivity (97.4%) of Gene Xpert MTB/RIF assay in smear-positive samples across all sample types [
In the current study, the highest proportion (about 71%) of smear-negative but Gene Xpert MTB/RIF assay positive results could be partially ascribed to performing smear microscopy directly on unprocessed sample. In our cohort, although the performance of smear microscopy was clearly inferior to that of Xpert MTB/RIF, no false positive smear results were observed. In our opinion, Xpert MTB/RIF assay should be considered as an adjunct test for improved case detection in smear-negative EPTB suspects in low income settings like Ethiopia, instead of replacing smear microscopy.
In the current study, sociodemographic characteristics like sex, age, marital status, and occupation were not significantly associated with EPTB infection; similar findings were reported in Gonder, Ethiopia [
Our results also demonstrated that smoking was not associated with EPTB which is consistent with other studies [
Our study has some limitations. Firstly, being conducted in hospital might not reflect reality of the community but it gives valuable information on burden of EPTB as well as importance of MDR-TB screening of EPTB cases in the study area. Although HIV infection is known risk factor for increasing EPTB infection, HIV status was not known in substantial number of EPTB suspected cases. However, this is quite important to be investigated with another future research. The present study employed only fluorescence staining technique and Gene Xpert MTB/RIF assay which have generally low sensitivity in comparison with culture, which is the gold standard for detection of EPTB due to paucibacillary nature of specimens and thus may underestimate the prevalence EPTB among the study cohorts.
The prevalence of Gene Xpert MTB/RIF assay and LED-FM confirmed EPTB was 8.8% and 2.5%, respectively. The most prevalent type of EPTB was TB lymphadenitis. Sociodemographic characteristics and lifestyle factors did not show significant association with EPTB. However, a previous history of pulmonary tuberculosis infections was significantly associated with Gene Xpert MTB/RIF assay confirmed EPTB. Discordant results were observed between LED-FM and Gene Xpert MTB/RIF assay with 71% (22/31) of smear-negative EPTB cases being Gene Xpert MTB/RIF assay positive and this needs developing strategies to enhance the sensitivity of FM microscopy for diagnosis of EPTB in resource limited countries like Ethiopia. Moreover, large scale study on the prevalence and risk factor of EPTB infection using culture or other more sensitive methods could help to determine the exact prevalence of EPTB infection in the study area.
Mycobacterium tuberculosis
Tuberculosis
Extrapulmonary tuberculosis
Pulmonary tuberculosis
Light-emitted diode
Fluorescent microscope.
The data used to support the findings of this study are included within the article.
The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
The authors declare that they have no conflicts of interest.
Yeshi Metaferia contributed to the design of the study, data acquisition and management, study supervision, analysis, interpretation of data, and manuscript preparation. Abdurahaman Seid contributed to study design, supervision, acquisition, analysis and interpretation of data, and manuscript preparation. Genet Molla Fenta contributed to study design, supervision, acquisition of data, and critical review of the manuscript. Daniel Gebretsadik contributed to study design, supervision, and critical review of the manuscript. All authors have edited and approved the final manuscript for publication.
The authors would like to acknowledge Wollo University for the approval of ethical clearance and funding support of this study. They also acknowledge South Wollo Zonal Health Bureau and Dessie Referral Hospital. The authors also express their gratitude to study participants, data collectors, and supervisors who participated in the study.