Comparative study between tuberculin skin test and serum albumin level in patients with active pulmonary tuberculosis

Background: Tuberculosis is difficult to diagnose and is an important cause of death among adults in developing countries. There is an urgent need for low-cost diagnostic markers in resource-limited settings. Aim: The aim of the study was to investigate the relationship between the intensity of the tuberculin test and serum albumin level in patients with active pulmonary tuberculosis. Patients and methods: Forty patients with active pulmonary tuberculosis before treatment were classified into two groups: group A and group B. Group A included 20 patients (17 men and three women; age 23-70 years) with serum albumin level below 3.5 g/dl. Group B included 20 patients (16 male and four female patients; age 15-68 years) with serum albumin level of 3.5 g/dl or more. Patients were subjected to full clinical evaluation. Comorbidities that may affect tuberculin reaction, such as HIV infection, alcoholism, chronic renal failure, and neoplasms, were excluded. Laboratory tests included complete blood count, evaluation of erythrocyte sedimentation rate, liver and kidney function tests, plain chest radiography, tuberculin skin test using the Mantoux technique, sputum test for acid fast bacilli by means of Ziehl-Neelsen staining for three consecutive days, and serum albumin level at the same time as the tuberculin test. Results: There was a statistically significant difference between the two groups as regards serum albumin level. The mean tuberculin skin test diameter in group A was 7.5 ΁ 3.94 mm and in group B was 20.9 ΁ 5.51 mm, which revealed statistically significant difference between the two groups. There was a statistically significant positive correlation between the intensity of tuberculin skin reaction at 72 h and serum albumin levels in both groups. Conclusion: Patients with active pulmonary tuberculosis and lower serum albumin levels have weaker skin responses to tuberculin test.


Introduction
Tuberculosis (TB, short for tubercle bacilli) is a common and often deadly infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis in humans. Tuberculosis usually attacks the lungs but can also aff ect other parts of the body [1].
Th e tuberculin skin test (TST) is a useful diagnostic test for evaluating individuals who have symptoms of tuberculosis or who are suspected of being infected with M. tuberculosis [2].
Th e TST is the standard test for the diagnosis of asymptomatic tuberculous infection. Tuberculin, a broth culture fi ltrate of tubercle bacilli, was fi rst prepared by Robert Koch in 1891. Subsequently, a standardized version of tuberculin, the purifi ed protein derivative, was introduced in 1934 [3].
Serum albumin is the most abundant protein in human plasma. Albumin is synthesized in the liver as preproalbumin. Th e rate of synthesis is dependent on protein intake, subjected to feedback regulation by plasma level, oncotic pressure, infl ammation, and hormones. During times of increased albumin loss, the liver can increase the rate of synthesis [4].
Hypoalbuminemia is a common problem among individuals with acute and chronic medical conditions; malnutrition is observed frequently in patients with pulmonary tuberculosis because of anorexia [5].

Aim of the work
Th e aim of the study was to investigate the possible relationship between the intensity of the TST reaction and serum albumin level in patients with active pulmonary tuberculosis.

Patients and methods
Th e study included 40 patients with active pulmonary tuberculosis just before initiation of treatment who were selected from the chest outpatient clinic, Benha University Hospital, during the period from March 2010 to December 2011. Th ey were classifi ed into two groups.

Comparative study between tuberculin skin test and serum albumin level in patients with active pulmonary tuberculosis
Ahmad A. Mohammad a , Osama E. Mohammad a , Abeer A. Shoman b Background Tuberculosis is diffi cult to diagnose and is an important cause of death among adults in developing countries. There is an urgent need for low-cost diagnostic markers in resource-limited settings.
Aim The aim of the study was to investigate the relationship between the intensity of the tuberculin test and serum albumin level in patients with active pulmonary tuberculosis.

Patients and methods
Forty patients with active pulmonary tuberculosis before treatment were classifi ed into two groups: group A and group B. Group A included 20 patients (17 men and three women; age 23-70 years) with serum albumin level below 3.5 g/dl. Group B included 20 patients (16 male and four female patients; age 15-68 years) with serum albumin level of 3.5 g/dl or more. Patients were subjected to full clinical evaluation. Comorbidities that may affect tuberculin reaction, such as HIV infection, alcoholism, chronic renal failure, and neoplasms, were excluded. Laboratory tests included complete blood count, evaluation of erythrocyte sedimentation rate, liver and kidney function tests, plain chest radiography, tuberculin skin test using the Mantoux technique, sputum test for acid fast bacilli by means of Ziehl-Neelsen staining for three consecutive days, and serum albumin level at the same time as the tuberculin test.

Results
There was a statistically signifi cant difference between the two groups as regards serum albumin level. The mean tuberculin skin test diameter in group A was 7.5 ± 3.94 mm and in group B was 20.9 ± 5.51 mm, which revealed statistically signifi cant difference between the two groups. There was a statistically signifi cant positive correlation between the intensity of tuberculin skin reaction at 72 h and serum albumin levels in both groups.
Group A: Th is group included 20 patients with serum albumin level below 3.5 g/dl and included 17 men (85%) and three women (15%), their ages ranging from 23 to 70 years. Group B: Th is group included 20 patients with serum albumin level of 3.5 g/dl or more and included 16 male (80%) and four female (20%) patients, their ages ranging from 15 to 68 years.

Inclusion criteria
Patients suff ering from active pulmonary tuberculosis (smear positive), defi ned as one or more initial sputum smear examinations positive for acid fast bacilli by microscopy, were eligible for inclusion into the study [6].
(2) HIV infection. All patients were subjected to the following: (1) Full history taking and physical examination. Special attention was paid to fever, cough, loss of weight and appetite, night sweats, weakness, and malaise, as well as to physical signs, such as pallor and weight loss, rales, and bronchial breathing. Th ree fi rst morning sputum specimens of 5-10 ml were taken after a deep productive cough for three consecutive days by asking the patients to cough into a sterile screw cap [7].Th e specimens were kept at 4°C before processing with N-acetyl-l-cysteine -NaOH (NALC-NaOH), for liquefaction, decontamination, and concentration [8]. (6) Serum albumin level at the same time as the tuberculin test.

Statistical analysis
Data were statistically analyzed using SPSS, version 16. Quantitative data were analyzed using mean and SD, whereas frequency and percentage were used for qualitative data. Th e Student t-test was used to compare means of diff erent groups, an d the χ 2 -test and the Z-test were used to compare frequencies. Pearson's correlation was used to ascertain relationships.
Statistical signifi cance was set at P values less than 0.05 [9].

Discussion
Th e TST is a useful diagnostic test for evaluating individuals who have symptoms of tuberculosis or who are suspected of being infected. A positive TST only indicates infection and by itself is not diagnostic of tuberculosis disease as it fails to distinguish between active disease and prior sensitization by contact wit h M. tuberculosis [10].
Malnutrition and tuberculosis are both problems of considerable magnitude. Th ese two problems tend to interact with each other, and the link between them has long bee n recognized. Malnutrition can lead to secondary immunodefi ciency, which increases the host's susceptibility to the development of clinical disease. In patients with tuberculosis, it leads to reduction in appetite, nutrition malabsorption, and altered metabolism [11].
In the present study 40 patients with active pulmonary tuberculosis were divided into group A and group B. Patients in group A had serum albumin level below 3.5 g/ dl and their ages ranged from 23 to 70 years, with a mean of 44.25 ± 15.55 years. Patients in group B had serum albumin level of 3.5 g/dl or more and their ages ranged from 15 to 68 years, with a mean of 35.3 ± 14.77 years. Th ere was no statistically signifi cant diff erence between the two groups as regards age distribution (Table 1).
Group A included 17 male patients (85%) and three female patients (15%) and group B included 16 male patients (80%) and four female patients (20%), revealing no statistically signifi cant diff erence (Table 2). Th e radiological classifi cation of the extent of the disease was as follows: in group A -minimal disease in 10 patients (45%), moderately advanced disease in seven patients (35%), and far advanced disease in three patients (15%); in group B -minimal disease in eight patients (40%), moderately advanced disease in eight patients (40%), and far advanced disease in four patients (20%). Th e results revealed no statistically signifi cant diff erence between the two groups (Table 3).
In this study serum albumin level in group A ranged from 1.5 to 3.4 g/dl, with a mean of 2.6 ± 0.48, and in group B it ranged from 3.5 to 4.5 g/dl, with a mean of 3.85 ± 0.33. Th ese results showed statistically signifi cant diff erence between the two groups ( Table 4). Th is result was in accordance with those of Michaelides et al. [12]. Th eir study included 48 patients with active pulmonary tuberculosis who were divided into group A, with low serum albumin (mean serum albumin level 2.95 ± 0.91) and group B, with normal serum albumin level (mean serum albumin level 3.92 ± 0.6).
Tuberculosis can cause diverse laboratory abnormalities suc h as anemia, increased erythrocyte sedimentation rate, and low serum albumin. Malnutrition per se has a more pronounced eff ect on serum albumin concentration in tuberculosis patients. Th us, all chronic infections such as tuberculosis can cause decreased production of serum albumin [13]. In the present study, TST diameter in group A ranged from 5 to 15 mm, with a mean of 7.5 ± 3.94 mm, and from 12 to 30 mm with a mean of 20.9 ± 5.51 mm in group B, which showed statistically signifi cant diff erence between the two groups (Table 5). Th is result was in agreement with tho se of Michaelides et al. [12]. In their study group A had low serum albumin and their mean TST diameter was 11.3 ± 2.1, and group B had normal serum albumin and their mean TST diameter was 18.4 ± 3.9, revealing statistically signifi cant diff erence between the two groups.
In our study there was a statistically signifi cant positive correlation between intensity of tuberculin skin reaction at 72 h and serum albumin levels in both groups (Figs 1 and 2). Th is result was in accordance with those of Kardjito and Donosepoetro [14], who studied the Mantoux test in tuberculosis. Th e result showed a statistically signifi cant positive correlation between intensity of tuberculin skin reaction and serum albumin levels.
Th is result was in accordance with those of Michaelides et al. [15], who studied the relationship between tuberculin hypersensitivity and serum albumin level in patients with pulmonary tuberculosis. Th eir study included 42 patients (35 males and seven females) aged 33.04 ± 15.7 years. Th e diameter of induration was 17.8 ± 6.01 mm and the serum albumin level was 7.27 ± 0.86 g/dl. Analysis showed a statistically signifi cant positive correlation between intensity of tuberculin skin reaction and serum albumin levels.
Th ese fi ndings indicated that tuberculous patients with lower albumin levels have weaker skin responses to tuberculin compared with those with normal albumin levels, which could be attributed to malnutrition, which causes suppression of delayed hypersensitivity reaction; false negative tuberculin reactions are very common in cases of advanced malnutrition, and malnutrition has been linked to decreased immune function [16].  Correlation between intensity of tuberculin skin reaction after72 hours and serum albumin levels in group A

Fig. 1
Tuberculin skin test and serum albumin level in patients with active pulmonary tuberculosis Mohammad et al. 191 Conclusion (1) Malnutrition is known to cause suppression of delayed hypersensitivity reaction. (2) Tuberculous patients with lower serum albumin levels have weaker skin responses to tube rculin. Correlation between intensity of tuberculin skin reaction after 72 hours and serum albumin levels in group B