A total of 200 patients were enrolled in this study, of which 103 (51.5%) were males and 97 (48.5%) were females, with the sex ratio of 1 man: 1 woman. Out of these 200 patients, 55 (27.5%) were aged ≥35 years while 145 (72.5 %) were aged <35 years. The mean age of the study population was 34.8 (±11.6) years ranging from 18-67 years. HIV test results were obtained from the 200 participants, of which 114 (57%) tested HIV positive and 86(43%) tested HIV negative. Of the 200 participants, 100 (50 %) were confirmed of having multidrug-resistant tuberculosis (MDR-TB) while the remaining 100 (50%) patients were diagnosed with drug-susceptible tuberculosis (DS-TB).
Sputum smear microscopy conversion rates and time-to-sputum conversion among HIV infected and uninfected patients:
Table 1 below depicts the proportions of smear microscopy grades at baseline stratified by HIV sero-status of the participants. HIV infected and uninfected patients were matched by their smear microscopy grades at enrolment (P = 0.79).
Table 1 Proportions of smear microscopy grades at baseline by HIV status
Baseline-smear grade HIV Positive HIV Negative P-value
n (%) n (%)
Scanty 7/14 (50%) 7/14 (50%) 0.79
+1 24/46 (52%) 22/46 (47%) 0.79
+2 24/41 (58.5%) 17/41 (41.5%) 0.79
+3 59/99 (59.6%) 40/99 (40.4 %) 0.79
After 4 and 8 weeks of appropriate anti-TB treatment, there was no statistically significant difference in the smear microscopy conversion rates of HIV infected patients as compared to HIV uninfected patients. However, Table 2 below shows that after 12 weeks of appropriate anti-TB treatment, although there was no statistically significant difference (X2 = 3.227; P=0.358) in the sputum smear conversion rates of HIV infected patients versus HIV uninfected patients, the conversion rate was however higher (>90%) among HIV infected patients whose baseline microscopy grade ranged from scanty to 2+ as compared to patients who had a grade of 3+ at baseline (conversion rate of 76%) (P = 0.049). In addition, after 12 weeks of treatment, there was also a significant microscopy conversion rate among DS-TB patients [43/45 (95.6%)] as compared to MDR-TB patients [54/69 (78.3%)] (P=0.009), all co-infected with HIV. Furthermore, among the HIV negative patients, data have also shown a significant microscopy conversion rate among DS-TB patients [48/55(69.6%)] as compared to MDR-TB patients [21/31(30.4%)] (P = 0.03).
Table 2. Proportions of negative cases (conversion rates) after 12 weeks of treatment according to HIV status
HIV Positive (n=114) HIV Negative (n=86)
Variables of Interest Smear Conv. P-value Smear Conv. P-value
Gender
Male 54/61 (88.5%) 0.20 35/42(83.3%) 0.33
Female 43/53 (81.1%) 0.20 34/44(77.3%) 0.33
Age
≥35 48/55(87.3 %) 0.36 32/35 (91.4 %) 0.27
<35 49/59 (83.1 %) 0.36 37/51(72.5 %) 0.27
Smear microscopy grade
Scanty 7/7 (100%) 0.049 7/7 (100 %) 0.28
+ 1 22/24 (91.7 %) 0.049 21/22 (95.5 %) 0.28
+ 2 23/24 (95.8 %) 0.049 14/17 (82.4 %) 0.28
+ 3 45/59 (76.3 %) 0.049 27/40 (67.5 %) 0.28
Baseline smear category
Scanty & +1 7/7(100%) 0.253 7/7(100%) 0.171
+2 & +3 90/107(84.1%) 0.253 62/79(78.5%) 0.171
TB status
MDR-TB 54/69(78.3 %) 0.009 21/31(67.7%) 0.030
DS-TB 43/45(95.6 %) 0.009 48/55(87.3%) 0.030
Smear Conv= Smear Conversion
Time to microscopy conversion was 4.58 ± 2.97 weeks and 5.69 ± 3.25 weeks for HIV positive patients aged ≥35 years and below 35 years respectively while among HIV negative patients, time to conversion was 5.00 ± 2.83 weeks and 6.86± 3.59 weeks for those aged ≥35 and below 35 years respectively (P = 0.003) as displayed in Figure 1 below.
Correlations between levels of HIV-associated immune suppression and time to microscopy conversion:
Of the 200 patients, 114 (57%) were HIV infected of which we only obtained CD4+ T cell count results from 51 patients. The mean CD4+ T cells for the 51 patients was 179.84 cells/mm3, ranging from 3 – 487 cells/mm3, with a standard error of the mean (SEM) of 19.59 cells/mm3 and standard deviation (SD) of 139.9 cells/mm3. Of the 51 HIV infected patients, 29 (56.9%) had CD4+ T cell count ≤200 cells/mm3 (severe immune suppression) while 17/51 (33.3%) and 5/51(9.8%) HIV infected patients had CD4+ T cell count of 200-349 cells/mm3 (advanced immune suppression) and 350-499 cells/mm3 (mild immune suppression), respectively.
All HIV infected MDR-TB patients who had a baseline CD4+ T cell count ≥350 cells/mm3 at the beginning of anti-TB treatment had a sputum microscopy conversion from positive to negative after 12 weeks. There was a significant correlation (P = 0.010) between the levels of immune suppression (CD4 count at the beginning of anti-TB therapy) and smear microscopy conversion rates after 12 weeks of appropriate treatment as depicted in Table 3 and Figure 2.
Table 3. Correlation between levels of immune-suppression by means of CD4 T cell count (cell/mm3) and sputum smears status among MDR-TB patients.
CD4 Category Converted Negative n (%) Remained positive n (%) P-Value
≤200 26/28 (92.9) 2/28 (7.1) 0.01
200 – 349 10/17 (58.8) 7/17 (41.2) 0.01
350 – 499 5/5 (100) 0 (0) 0.01
Time to conversion (in weeks) from smear microscopy positive to negative among the HIV+ co-infected with MDR TB is summarized in the Figure 3 below taking into account their levels of immune-suppression at the initiation of appropriate anti-TB therapy. All HIV patients who had the initial CD4 Count > 350 converted from sputum smear microscopy positive to negative. The patient whose CD4 Count was <200 Cells/mm3 had a conversion rate of 92.9 % after 10 weeks of anti-TB treatment as compare to patient whose CD4 count was between 200 to 349 Cells/mm3 who only achieved 60% conversion rate.
When the 51 HIV positive patients co-infected with MDR TB were categorized in two groups composed of Group 1: 28 (54.9%) patients with CD4 <200 cells/mm3 and Group 2: 23(45.1%) patients with CD4 ≥200 cells/mm3; although patients with CD4<200 cells/mm3 converted faster than those with CD4 ≥200 cells/mm3 this difference did not reach statistical significance (P=0.184) as depicted in the Figure 4 below.
Table 4 below depicts a significant correlation (P=0.015) between the levels of immuno-suppression (CD4 count at the beginning of anti-TB therapy) and smear microscopy conversion rates after 12 weeks of appropriate treatment. In addition, time to microscopy conversion rate was shorter (4.25±2.43) among HIV positive patients whose CD4 counts ≤200 as compared to those who had CD4 count between 200 – 349 (6.77 ±3.99) and 350 – 499 (7.40±2.97). These results can also be seen in Figure 5.
Table 4. Time to conversion between levels of immune-suppression by means of CD4 T-cell count (cells/mm3) and HIV status (P=0.0015)
CD4 Count n Mean SD (95% CI)
≤200 28 4.25 2.43 (3.31 – 5.19)
200 -349 17 6.77 3.99 (4.71 – 8.82)
350-499 5 7.40 2.97 (3.72 – 11.08)
Prolongation of smear positivity in all TB patients at 12 weeks post-anti-TB initiation:
Using bivariate analysis, Table 5 shows that at end of 12 weeks of appropriate anti-TB therapy, patients aged <35 years (P=0.045), who had 2+ to 3+ baseline grade smear microscopy (P<0.0001) and diagnosed with MDR-TB (P=0.003), were significantly associated with a prolongation of smear positivity.
Figure 6 shows that at the end of 12 weeks of anti TB therapy, 9% of DS-TB patients remained positive versus 25 % of MDR-TB counterparts (P=0.003). However, Figure 7 shows that 87.9% of MDR TB patients who are aged ≥35 years converted negative at the end of 12 weeks of anti TB therapy as compared to 78.2% of MDR Tb patient aged < 35 years (P=0.045).
Table 5 Factors associated with prolongation of smear positivity in all TB patients at 12 weeks post-anti-TB initiation
Variable of interest Converted negative n (%) P-Value
Gender 0.186
Male 89 (86.4)
Female 77(79.4)
Age 0.045
≥35 80(87.9)
<35 86(78.2)
Baseline smear microscopy <0.0001
Scanty 14 (100)
+1 43(93.5)
+2 37(90.2)
+3 77(72.7)
TB susceptibility 0.003
MDR-TB 75(75)
DS-TB 91(91)
HIV status 0.365
Positive 97(85.1)
As depicted in Table 6 and Figure 8, time to microscopy conversion from positive to negative was significantly influenced by the baseline smear grade result (p < 0.0001).
Table 6 Time to negative conversion in weeks by baseline smear microscopy for all patients diagnosed with TB (P<0.0001)
Smear grade n mean SD (95 % CI)
Scanty 14 3.86 2.07 (2.66 – 5.05)
+1 46 3.78 1.60 (3.41 – 4.26)
+2 41 5.83 2.70 (4.98 – 6.68)
+3 99 6.53 3.80 (5.77 – 7.28)
Table 7 below shows proportions of time to microscopy conversion rates over time among HIV infected and HIV uninfected TB patient receiving anti TB treatment. The proportions of TB patients who had negative microscopy results were not statistically significant after 4, 8 and 12 weeks.
Table 7 Time to microscopy conversion rates in weeks by HIV status
HIV Positive HIV Negative
Treatment duration Converted Remained Converted Remained P-Value
Negative Positive Negative Positive
4 weeks 64 (56.1%) 50 (43.9%) 49(57%) 37(43.0%) 0.688
8 weeks 96 (84.2%) 18 (15.8%) 69(80.2%) 17 (19.8%) 0.800
12 weeks 97 (85.1%) 17(14.9%) 69(80.2%) 17 (4.7%) 0.358
Prolongation of smear positivity at 12 weeks post-anti-TB initiation in patients diagnosed with MDR-TB as compared to patients diagnosed with drug susceptible TB:
In bivariate analysis, Table 8 below shows that baseline smear microscopy grade (P=0.014) and initial CD4 T cells category (P=0.010) were significantly associated with the prolongation of smear positivity in MDR-TB patients (versus DS-TB patients) at the end of 12 weeks’ post-therapy.
In addition, time to microscopy conversion in patients diagnosed with MDR-TB was significantly prolonged as compared to patients diagnosed with DS-TB irrespective of their HIV status (P=0.001) as shown in Table 9 and Figure 9 below.
Table 8 Factors associated with prolongation of smear positivity at 12 weeks post-anti-TB initiation in patients diagnosed with MDR-TB as compared to patients
|
MDR-TB patients
|
DS-TB patients
|
Variables of interest
|
Converted negative (%)
|
Remained positive (%)
|
p-value
|
Converted negative (%)
|
Remained positive (%)
|
p-value
|
Gender
Male
Female
|
41/52 (78.8)
34/48 (70.8)
|
11 (21.2)
14 (29.2)
|
0.355
|
48/51 (94.1)
43/49 (87.8)
|
3(5.9)
6(12.2)
|
0.266
|
Age, years
≥35
<35
|
35/42 (83.3)
40/58 (69.0)
|
7 (16.7)
18 (31.0)
|
0.101
|
45/48 (93.8)
46/52 (88.5)
|
3 (6.3)
6 (11.5)
|
0.356
|
Baseline smear
Scanty
+1
+2
+3
|
8/8 (100)
15/17 (88.2)
13/14 (92.9)
39/61 (63.9)
|
0 (0)
2/17 (11.8)
1/14 (7.1)
22/61 (36.1)
|
0.014
|
6/6 (100)
28/29 (96.6)
24/17 (88.9)
33/38 (86.8)
|
0 (0)
1/29 (3.4)
3/27 (11.1)
5/38 (13.2)
|
0.452
|
Baseline smear
Scanty and +1
+2 and +3
|
8/8 (100)
67/92 (72.8)
|
0 (0)
25/92 (27.2)
|
0.089
|
6/6 (100)
85/94 (90.4)
|
0 (0)
9/94 (9.6)
|
0.427
|
CD4+ T cell groups
< 200 cells/µl
≥ 200 cells/µl
|
26 (92.9)
49 (68.1)
|
2 (7.1)
23 (31.9)
|
0.010
|
-
|
-
|
-
|
HIV status
Positive
Negative
|
54/69 (78.3)
21/31 (67.7)
|
15 (21.7)
10 (32.3)
|
0.261
|
43/45 (95.6)
48/55 (87.3)
|
2/45 (4.4)
7/55 (12.7)
|
0.150
|
Table 9 Time to microscopy conversion (weeks) by HIV status in MDR-TB patients versus DS-TB patients (P=0.001)
HIV & MDR status n Mean SD (95 % CI)
HIV (-) & MDR (-) 55 5.49 2.99 (4.68 – 6.30)
HIV (-) & MDR (+) 31 7.19 3.87 (5.78 – 8.61)
HIV (+) & MDR (-) 45 4.13 1.99 (3.53 - 4.73)
HIV (+ ) & MDR (+) 69 5.83 3.59 (4.97 – 6.69)
Furthermore, among MDR-TB patients, time to microscopy conversion in patients aged <35 years was significantly prolonged as compared to patients aged >35 years (P=0.004) as shown in Table 10 and Figure 10 below.
Table 10 Time to conversion in week by age category (P=0.004)
Ages (years) n Mean SD (95 % CI)
18 – 24 41 6.88 3.50 (5.78 – 7.98)
25 – 34 69 5.86 3.39 (5.04 – 6.67)
35 – 44 52 4.94 2.97 (4.12 – 5.77)
≥45 38 4.47 2.84 (3.54 – 5.41)
In multivariate analysis, Cox regression showed that only the baseline smear microscopy grade was independently associated with prolonged smear positivity in MDR-TB patients at 12 weeks (ρ = 0.014), after adjusting for HIV status, CD4 count and age. As depicted in Figure 11, Cox regression analysis has shown that at the end of 8 weeks on anti TB therapy, all MDR TB patients who had a baseline smear microscopy form scanty to +1 converted negative whilst 25% of patients with +2 and +3 remained positive until the end 12 weeks of treatment (P=0.014).