The relationship between computed tomography appearance of pulmonary tuberculosis and blood glucose levels in 763 diabetes mellitus patients with pulmonary tuberculosis: a comparative study

After the selection of including and excluding criteria, a total of 763 DMTB patients were included in the study (Table 1). CT scores were found to be positively associated with serum levels of cholesterol, TG, and LDL and their levels reached the highest level in the high-CT-score group (Table 1, P < 0.0001). CT scores were also found to be positively associated with the levels of leukocytes and lymphocytes, and their levels reached the highest level in the high-CT-score group (Table 1, P < 0.0001). CT scores were affected by TB and type-II DM duration (Table 1, P < 0.0001). Furthermore, the uncontrolled/controlled type-II DM cases (ratio) were 65/196 (0.33), 189/207 (0.91) and 69/37 (1.86) (Table 1, P < 0.0001) from low-, middle- and high-score groups, respectively. The results suggest that high CT scores are closely associated with the ratio of uncontrolled/controlled type-II DM cases.

The statistical differences were insignificant for other parameters, including gender distribution, smoking, the cases of chronic renal failure, previous history of malignancy, connective tissue disease, previous history of organ transplantation and serum HDL levels (Table 1, P > 0.05).

Among all the patients, solitary pulmonary nodules (SPNs) were the most prevalent diagnostic CT abnormality but the size of most SPNs was less than 1 cm and their numbers were more than 5. The number and size of cavities in the high-CT-score group were more than those in the middle-CT-score and low-CT-score group (Table 2, P < 0.0001), and the diameter size of most cavities was less than 3 cm. The size of cavities (diameters (cm), median (95% CI of median)) was 0.72 (0.66–0.77), 1.20 (1.09–1.28), and 3.45 (2.92–3.94) from the low-, middle- and high-CT-score groups, respectively (Table 2). The incidence of bronchiectasis, TB consolidation, and cluster micronodules in the high-CT-score group were more than those in the middle-CT-score and low-CT-score group (Table 2, P < 0.0001). The statistical differences were insignificant among the three groups for the incidence of tree-in-bud lesions, centrilobular micronodules, pleural effusion, small airway wall thickening, ground-glass opacities and random micronodules (Table 2, P > 0.05). Nodules (> 1 cm), interlobular septal thickening and reversed halo signs were not found in all patients (Table 2).

The severity of TB is difficult to be displayed by using a unique criterion. In the present study, the severity of TB was presented by using CT scores via the combination of typical CT findings and atypical CT findings according to the previous report [15]. In the low-CT-score group, TB patients had a lower incidence of upper lung field lesions in comparison with lower lung field lesions (42 cases, 16.1% vs. 153 cases, 58.6%, respectively, P < 0.0001). The differences for the distribution ratio were also found in the middle-CT-score group (87 cases, 22.0% vs. 213 cases, 53.8%, respectively, P < 0.0001) and the high-CT-score group (23 cases, 21.7% vs. 60 cases, 56.6%, respectively, P < 0.0001). With the CT scores increasing, the lesion expanded more lung fields and the upper lung field increased (Fig. 2). In this sense, upper lung field lesions were more likely to exist in patients with middle-CT and high-CT scores. On the other hand, for lower lung field, as well as for upper + lower lung fields, the statistical differences were insignificant in the incidence of unilateral/bilateral lesions among all groups (Fig. 2, P = 0.415).

Pulmonary cavities are the definitive mark of TB and the sites with high mycobacterial burden because of drug resistance and treatment failure [18]. However, pulmonary cavities were seldomly found in the low-CT-score group (Fig. 2A, 7 scores and Fig. 2B, 6 scores). Pulmonary cavities were mostly found in middle-CT-score and high-CT-score groups. In some cases, the diameter of the cavity was more than 3 cm and the thickness of the cavity was more than 1 cm (Fig. 2C, 9 scores). Multiple cavities were often found in the middle-CT-score group (Fig. 2D, 12 scores, 3 cavities with the diameters of 2.6 cm, 1.8 cm, and 1.3 cm, respectively. The thickness of cavities is 0.3 cm, 0.5 cm and 0.3 cm, respectively). The larger size of cavities was often found in high-CT-score group (Fig. 2E, 15 scores, 3 cavities; One cavity was located in the right upper lobe with a length of about 1.1 cm and a thickness of 0.5 cm; One cavity was located in the left upper lobe cavity with a length of about 1.7 cm and a thickness of about 0.5 cm; One cavity was located in the left lower lobe with a length of about 4.9 cm and a thickness of about 0.4 cm). In some cases, the size of cavity was more than 7 cm in the high-CT-score group (Fig. 2F, 13 scores, the diameter of cavity was 7.6 cm and its thickness was 0.9 cm). These results suggest that cavity occurrence is the predominant factor for increasing the scores of TB. Multiple cavitary lesions were relatively frequent in the middle-CT-score and high-CT-score groups. CMs exhibit large nodular opacity and are active TB [15], and found in almost half of the patients (364 cases, 47.7%, Fig. 2A, E, F).

Blood glucose levels (2FBG) in the high-CT-score TB group (mean 13.48 mM, 95% CI of median 12.56–14.44 mM) were higher than in the middle-CT-score TB group (mean 10.16 mM, 95% CI of median 9.89–10.49 mM), whose blood glucose levels were also higher than the low-CT-score TB group (mean 8.73 mM, 95% CI of median 8.49–9.36 mM) (Fig. 3A, P < 0.0001). The Pearson Correlation Coefficient is the methodology normally used for linear variable selection. The analysis showed that blood glucose level was increased with the CT score increasing and had a consistent relationship with the CT scores since the rho value was 0.6 (Fig. 3B, P < 0.0001). Pearson correlation coefficient analysis showed that DM duration had a weak but positive correlation with CT scores because the rho value was 0.27 (P < 0.0001) [19].