Pulmonary tuberculosis (TB) is a global health problem. It affects all ages and is present in almost all countries. According to a recent WHO factsheet, TB comes second, after COVID-19, as a leading killer caused by a single infectious agent.[1] About 1.5 million patients died from TB, and 10 million got the disease in 2020.[1] In Sudan, the incidence per 100,000 population declined gradually over the past 10 years to reach 67 in the year 2019.[2]

Malnutrition is a common problem in low-income counties in Sub-Saharan Africa.[3] It is a recognized risk factor of TB as it adversely affects the immune system and increases the body susceptibility to infections.[4] It is estimated that the TB cases attributed to malnutrition could be higher than the cases attributed to the human immunodeficiency virus (HIV), which indicates the importance of malnutrition as a risk factor of the disease.[5] However, malnutrition may develop as a complication of TB and could be associated with delayed recovery and higher mortality rates than the well-nourished patients.[6]

Several studies reported weight loss and wasting in patients with active pulmonary TB. The loss of weight is caused by reduced protein intake, reduced gastrointestinal absorption of nutrients, and increased metabolism associated with inflammation.[7] Coinfection with other infectious agents like the HIV would aggravate the condition.

Anemia in TB patients is a common finding with variable prevalence. It could be caused by many factors, especially malnutrition, malabsorption, and bone marrow suppression due to chronic inflammation. Both normocytic normochromic and microcytic hypochromic anemia were reported.[8] Screening for anemia in patients with active pulmonary TB and determination of its cause is an important step in the TB management.

The aim of this study is to evaluate the nutritional status of Sudanese patients with sputum- positive pulmonary tuberculous and to describe their anemia patterns at the time of presentation.

This cross-sectional hospital-based study was carried out for 6 months in Al Shaab Hospital, a tertiary-level cardiothoracic center in Sudan. Ethical clearance was sought from the hospital ethics committee. All patients gave their informed consent before participating in the study. The study included 100 newly diagnosed tuberculous patients of both sexes above the age of 16-year old. Patients were referred to the hospital with a professional diagnosis of pulmonary TB and positive microscopic results of sputum stained for acid-fast bacilli. Patients with chronic medical illnesses, including liver disease, renal impairment, malignancy, pregnancy, and diabetes mellitus and those who experienced a major hemorrhage during the past 3 months of the study and those on tonics were excluded from the study.

The weight and height of each patient were measured using a standardized weight and height scale. The body mass index (BMI) was calculated in kg/m[2]. The skin fold thickness was measured from multiple sites (triceps, suprailiac, and thigh) for females and (pectoral, abdominal, and thigh) for males, using the Holtain skin caliper. The percentage of total body fat (BF%) was calculated using the Jackson–Pollock and Siri equations.[9] Blood samples were collected from each patient for conventional complete blood count, renal function test, and liver function tests. Patient's urine was screened for proteinuria. Anemia was defined as a hemoglobin level <13 g/dl in males and <12 g/dl in females. A rapid immunochromatographic test was used for the qualitative detection of HIV infection.

A data collection form was used to collect demographic information and register the test results of each participant. The results were then analyzed using the Statistical Package for the Social Sciences (SPSS), V 20, IBM Corp., Armonk, NY, USA. Differences between proportions were tested using the Chi-square test. A P < 0.05 was considered statistically significant.

The study included 100 patients with active pulmonary TB in the age range 16–74-year old. The majority of the participants (61%) were in the age group 21–40-year old, with a mean age of 33.47 ± 12.98 years. The male-to-female ratio was 2:1 [Table 1]. The majority of males (91.2%) and females (84.4%) had low BF%, and only 8.8% and 15.6% had adequate BF% for their ages, respectively [Table 1].

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About 62% of the participants were underweight, 34% had normal BMI, and 4% were overweight [Table 2]. Those who had symptoms for more than 3 months showed a higher percentage of low weight than those who had symptoms for a shorter duration (19.3% vs. 11.8%, respectively). The relation between the BMI groups and chronicity of the illness was statistically significant (P < 0.001) [Table 2].

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Eighty percent of all participants had anemia (76% of males and 87% of females). The major morphological type of anemia was microcytic hypochromic (90%). Only 10% showed normocytic normochromic anemia. The macrocytic type was not detected [Table 3].

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Low serum albumin was found in 21% of the tuberculous patients. Statistical analysis showed insignificant relation of serum albumin to proteinuria [Table 4].

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Pulmonary TB is an infectious disease that carries high morbidity and mortality. It imposes a major burden on the health-care system in Sudan. In our sample, the finding that males outnumbered the females in a ratio of 2:1 is consistent with the worldwide prevalence of the disease. The WHO reported in 2020 that adult men were 56% of all TB cases, women 33%, and children 11%.[1] Similarly, as described in the same WHO report, the majority of patients were within the most productive age groups <40 years old. This could explain how TB affects the economics and development of this country.

Primary malnutrition, through its adverse effects on the immune system of malnourished patients, is a known predisposing factor of TB as well as many other infectious diseases.[4] It is also associated with higher mortality rates and reactivation of a latent disease.[10]

On the other hand, TB is a chronic inflammatory disease that causes weight loss through its effects on food intake, food absorption, and increased rate of metabolism.[7] A distinct inflammatory profile related to anemia of pulmonary TB was recently reported.[11] The authors described sustained increased levels of inflammatory markers, including C-reactive protein, that may persist for 2 months after the initiation of the pharmacological treatment.

In this study, the majority of the participants showed low BF% for their ages, and about 62% were underweight. It is recognized that being underweight is an indicator of malnutrition; however, it is unknown whether that is a cause or a sequel of pulmonary TB. The study showed a significant association between being underweight and a longer duration of the disease, which is highly suggestive of malnutrition being a result of pulmonary TB. A previous study showed that participants who receive adequate nutritional support during TB treatment tend to gain more weight when compared to those who continue to take a poor diet during the treatment.[12]

Opposite to the fact that chronic respiratory diseases are commonly associated with secondary polycythemia because of the associated hypoxia; anemia in pulmonary TB is highly prevalent.[8] The possible causes could be bone marrow suppression by the inflammatory markers or deficiency of macro- and micronutrients due to malnutrition. Other causes of anemia are also possible, especially chronic bleeding through coughing of the large amount of blood that would result in iron deficiency anemia. The prevalence of anemia in this study is very high (80%). Our finding is that the most prevalent pattern is microcytic hypochromic anemia is indicative of iron deficiency, which could be associated with coughing of blood, malnutrition, or both. Other studies reported a higher prevalence of normocytic normochromic anemia (56.9%) compared to microcytic hypochromic anemia (28.7%);[8] however, the majority of tuberculous patients in this study had normal weight. The same study showed a low prevalence of megaloblastic anemia, which goes with our findings.[8] It is worth noting that antituberculous drugs such as isoniazid and pyrazinamide are possible causes of anemia through their interference with Vitamin B6 activity, but our participants were newly diagnosed patients with a short history of treatment.

Low serum albumin is a recognized finding in malnourished patients. As low serum albumin might be caused by renal disease, the insignificant association of hypoalbuminemia and proteinuria in this study excludes this possibility.

About 62% of the patients, who were hospitalized for treatment of active pulmonary TB, had signs of malnutrition that were significantly related to the duration of the disease. The majority (80%) of the tuberculous patients had anemia. The most common type of anemia in these patients was microcytic hypochromic. These findings might be considered in the management plan of tuberculous patients.

Limitations of the study

The present study has few limitations that should be considered for the appropriate interpretation of the results. Poor nutrition as a possible cause of weight loss was not assessed among the tuberculous patients. The duration of tuberculous symptoms could be more than what was reported by each patient. Other associated medical illnesses could not be completely ruled out with limited biochemical investigations.

Ethical statement

The study was approved by the institutional Ethics Committee of Al Shaab Teaching Hospital (Approval No.2020/21).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.