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Effectiveness of RHZE-FDC (fixed-dose combination) compared to RH-FDC + Z for tuberculosis treatment in Brazil: a cohort study

BMC Infectious Diseases201515:81

https://doi.org/10.1186/s12879-015-0820-4

Received: 30 June 2014

Accepted: 10 February 2015

Published: 21 February 2015

Abstract

Background

In 2009, Brazil was the sole high-burden country to use three drugs [rifampin (R), isoniazid (H) and pyrazinamide (Z)] as the standard treatment for sensitive tuberculosis, with RH in fixed-dose combination (FDC). In December 2009, the country has adopted the FDC four-drug regimen including ethambutol (E). The rationale was the expectation to reduce default and resistance rates, by increasing adherence to treatment and avoiding monotherapy. However, there is no consensus on the superior effectiveness of the RHZE-FDC regimen over RH-FDC + Z. In particular, few studies evaluated its influence on default and smear negativation rates.

Methods

We conducted a historic cohort study to assess the effectiveness of RHZE-FDC for the treatment of tuberculosis in Brazil, measured by the rates of treatment default and smear negativation in the second month of treatment, using secondary data from the national information system known as SINAN-TB.

Results

The RHZE-FDC had a protective effect against treatment default compared to RH-FDC + Z, reducing it by 14%. However, it was not possible to show an effect of the RHZE-FDC on the rate of second month smear negativation. In addition to the regimen, other well-studied individual characteristics, such as older age (over 38 years) and higher education occupation were also protective against default. Conversely, alcoholism increased the probability of defaulting. These programmatic findings suggests the benefits of RHZE-FDC over RH-FDC + Z.

Conclusion

Our analysis of a cohort database in a high burden country shows that compared to RH-FDC + Z, RHZE-FDC reduces the default rates, independently of other influencing individual or health service factors.

Keywords

Effectiveness Fixed-dose combination Treatment Tuberculosis

Background

Tuberculosis is a public health problem in Brazil. The country is part of the list of the 22 high-burden countries since its first edition [1], despite the recent advances in the control of the epidemics: incidence rates decreased from 47 in 2001 to 36 new cases/100,000 inhabitants in 2012. Nevertheless, cure (79%) and default (12%) rates remain way beyond those needed to attain the millennium development goals up to 2050 [2], to which the Brazilian Ministry of Health (MoH) committed [3].

The advances in tuberculosis control, despite insufficient, were obtained after the adoption of a few strategies by the MoH [4]. Treatment for tuberculosis is free of charge in the country and includes the short regimen with rifampin since the seventies. Since the eighties, the MoH has strengthened the primary care services, and since the nineties, adopted the Family Health Strategy [5]. Additionally, the directly observed therapy (DOT) was recommended nationally [6].

However, to face the challenge of further improvement of operational tuberculosis indicators, new strategies were proposed. In the end of 2009, in the hope of reducing the rates of treatment default and halting the possible increase in resistance rates, the Brazilian National Tuberculosis Program (NTP) recommended the adoption of the World Health Organization (WHO)-recommended regimen: Rifampin (R), Isoniazid (H), Pyrazinamide (Z) and Ethambutol (E) in fixed-combined doses (2RHZE-FDC/4RH-FDC) as replacement for the 2RH-FDC + Z/4RH-FDC in use at that time. This change was recommended for adults and adolescents over 10 years [7]. It was expected that the FDC presentation would increase treatment effectiveness by reducing default because of the smaller number of pills to be swallowed and because of possible better tolerance, since standard doses of H and Z for those weighting over 50 kg were reduced from 400 to 300 mg and from 2000 to 1200 mg, respectively [8]. Additionally, the NTP expected to halt the increase in resistance because the possibility of monotherapy would be avoided. Moreover, the addition of E was expected to decrease failure among patients with suspected H-resistant TB. Despite the alarming increase in multidrug-resistant tuberculosis in many parts of the world, resistant rates remain low in Brazil. Finally, an easier administration of drug supply was expected with the “new” regimen.

However, there is no consensus in the literature on the higher efficacy of the FDC regimen when compared to separate drug regimens for treating tuberculosis. The higher efficacy of the RHZE over RHZ is also poorly studied, mainly in countries having adopted it recently. Three systematic reviews (SR) on FDC versus separate drug regimens for tuberculosis treatment are available [9-11]. In the recently published (2013) SR by Albanna et al. [9] that included 15 randomized control trials (RCT), FDC was not associated with reduction in failure, relapse, two-month smear/culture positivity (an early surrogate for cure), or emergence of drug resistance as compared to separate drug formulation. Out of five RCTs that evaluated adherence, none favoured FDC formulations.

Monedero & Caminero [11] also concluded that regarding cure and relapse rates, the FDC are not superior to separate drugs for treating tuberculosis. Only one out of the 15 included studies evaluated prevention of resistance, and other important outcomes, such as default rates and two-month smear negativation, were not evaluated in these studies. The authors concluded that the FDC regimen should be recommended for logistic reasons, costs and practicability, but not on effectiveness grounds.

The third SR, dated 2004, is a more generic review of FDC treatments and included two studies on tuberculosis [10], which did not corroborate the superiority of this regimen.

Thus, little information is available on the effectiveness of the RHZE-FDC in high burden countries that have already adopted other strategies, such as DOT and decentralization for tuberculosis control. The present study aimed to evaluate the effectiveness of RHZE-FDC compared to RH-FDC + Z for tuberculosis treatment in Brazil, using a historical cohort database with secondary data from the national surveillance information system (Sistema de Informação de Agravos de Notificação da Tuberculose – SINAN-TB). Outcomes were treatment default and negativation of smears at the second month of treatment.

Methods

We conducted a non-concurrent cohort observational study to evaluate the effects of interventions applied to subjects diagnosed and treated in Brazilian health care units from five cities. In Brazil, tuberculosis is a compulsorily notified disease and both diagnosis and treatment are provided free of charge in the public national health system (Sistema Único de Saúde-SUS). There are no individual selection criteria for the use of any tuberculosis treatment regimen in new cases in Brazil. The NTP distributes the drugs to the State and Municipal Health Departments, which distribute to health units upon case notification. The adoption of FDC was a programmatic decision and its implementation was progressive, during our study period. Once the health unit implements the regimen, all patients will receive the same treatment. Other regimens will only be available for intolerance or resistance.

We selected new tuberculosis cases (untreated previously) who started treatment from October 2009 to September 2010, residents in five eligible cities according to the following criteria: (i) cities in the five geographical regions of the country; (ii) with at least 120 notified cases yearly; (iii) with different incidence rates (over and above the national incidence rate) e (iv) with different proportions of cases using RHZE-FDC (under 30%, between 30 and 70% and over 70%) during the study period.

Based on these criteria, the following cities were selected by convenience: Goiânia (Central region, low incidence), Manaus, Salvador and Porto Alegre (high incidence, over 70% use of FDC-RHZE in the North, Northeast and South regions, respectively) and Rio de Janeiro (high incidence, under 30% of FDC-RHZE use, Southeast region).

Since besides individual characteristics, health service-related characteristics can influence the outcomes of this kind of intervention, both were collected and analysed as independent variables in a hierarchized model. Individual variables present in SINAN and included in our analyses were: (a) sex, (b) age group, (c) schooling, (d) occupation, (e) living in prisons, (f) alcoholism, (g) diabetes, (h) mental disease, (i) HIV infection, (j) other co-morbidities and (k) DOT. Health care service-related variables were: (1) facilities treating more than 125 cases yearly, (2) DOT implemented in the unit, (3) follow-up smears requested in the unit, (4) units having their own laboratorial facilities, (5) complete health team, including physician, nurse and social worker, (6) units with a social service, (7) units with community health care agents, (8) units with the Family Health Strategy, (9) units with training activities, (10) units with primary care services (11) units having exclusively primary care. These facility-related data were extracted from the National Registry of Health Care Units (Cadastro Nacional de Estabelecimentos de Saúde), available at cnes.datasus.gov.br, accessed on July 12 2012, and validated with the municipal tuberculosis program by one of the authors.

The notification system allows entry of separate drugs used for the treatment of tuberculosis. Until the adoption of the FDC-RHZE treatment, E was not used in the country for new cases, only for retreatment cases. Hence, we considered that reported new cases using E after the implementation of RHZE-FDC in the city were using the FDC formulation. Likewise, registries of new cases using R, H and Z only were considered to be using the previous RH-FDC + Z regimen.

The effectiveness was evaluated using two outcomes: default (according to the NTP guidelines, 30 days without treatment or 60 days without follow up) and negativation of smear at the second month of treatment (a hallmark for deciding on treatment change according to the National Guidelines) [8]. Both treatment outcomes were obtained in the follow-up SINAN database. Details on the quality of the SINAN database during the study period are available elsewhere [12]. In summary, a previous quality evaluation including completeness and consistence criteria had shown that the database was suitable for this kind of analysis.

A hierarchized logistic regression model was used considering two levels, the individual and the collective. The final model originated from the specific models for each of both levels. A significance cut-off of 0.2 was considered to include variables from the specific level models. Using the stepwise method, the final model considered a 0.05 significance cut-off.

The use of the tuberculosis surveillance database was authorized by the Brazilian NTP under confidentiality condition. The study was approved by the Institutional Review Board of the Social Medicine Institute of Rio de Janeiro State University and by the National Ethical Committee (25000.219561/2011-72). Since this study was based on secondary data, routinely collected and registered in the national surveillance information system, informed consent was not obtained from individual patients. The ethical boards were aware and exempted from the consent procedure. The intervention (treatment with RHZE-FDC) was not the researchers decision, we just documented the differences between patients, services and cities having implemented the recommended regimen or not.

Results

A total of 11,111 patients were included, of whom 46% were residents in Rio de Janeiro, situated in the Southeast region, which concentrates more than half the Brazilian population; 23% in Salvador, 14% in Manaus and Porto Alegre each and 3% in Goiânia. Table 1 shows the distribution of patients in the cities according to the type of treatment.
Table 1

Distribution of pulmonary tuberculosis patients per city according to the type of treatment from October 2009 to September 2010

City

FDC-RHZE

RH-FDC + Z

Total

 

N

%

N

%

N

%

Goiania

120

41.5

169

58.5

289

100.0

Manaus

1181

75.1

391

24.9

1572

100.0

Porto Alegre

859

54.3

724

45.7

1583

100.0

Rio de Janeiro

205

4.0

4942

96.0

5147

100.0

Salvador

1372

54.4

1148

45.6

2520

100.0

Total

3737

33.6

7374

66.4

11111

100.0

FDC = fixed-dose combination; R = rifampin; H = isoniazid; Z = pyrazinamide; E = ethambutol.

Patients who received the RHZE-FDC regimen were more likely to be older, illiterate, alcoholics, have other co-morbidities considering a 0.05 significance level; while those under RH-FDC + Z were more likely to be in prisons (Table 2). These differences indicated that patients’ heterogeneity should be taken into account in the evaluation of the effect of the intervention on the outcomes. They could be also due to differences overtime, since RHZE-FDC patients corresponded to more recent notifications in the same city.
Table 2

Characteristics of pulmonary tuberculosis patients according to the type of treatment from October 2009 to September 2010

Characteristics

FDC-RHZE

RH-FDC + Z

Total

p-value

 

N

%

N

%

N

%

 

Age

       

  <38 years

1952

52.2

4100

55.6

6052

54.5

0.001

  ≥38 years

1785

47.8

3.274

44.4

5059

45.5

 

  Total

3737

 

7374

 

11111

  

Sex

       

  Feminine

1301

34.8

2539

34.4

384

34.6

0.689

  Masculine

2436

65.2

4835

65.6

7271

65.4

 

  Total

3737

 

7374

 

11111

  

Illiteracy

       

  No

3487

96.4

7035

97.4

10522

97.0

0.003

  Yes

132

3.7

189

2.6

321

3.0

 

  Total

3619

 

7224

 

10843

  

Higher education occupation

       

  No

2773

97.0

5488

96.6

8261

96.7

0.384

  Yes

87

3.0

193

3.4

280

3.3

 

  Total

286

 

5681

 

8541

  

Living in prisons

       

  No

3362

91.8

6320

87.9

9682

89.2

0.000

  Yes

302

8.2

869

12.1

1171

10.8

 

  Total

3664

 

7189

 

10853

  

Alcohol use

       

  No

2835

81.8

5256

85.8

8091

84.3

0.000

  Yes

632

18.2

870

14.2

1502

15.7

 

  Total

3467

 

6126

 

9593

  

Diabetes

       

  No

3174

92.4

5505

91.6

8679

91.9

0.174

  Yes

262

7.6

505

8.4

767

8.1

 

  Total

3436

 

6010

 

9446

  

Mental disorder

       

  No

3363

97.8

5896

97.4

9259

97.5

0.194

  Yes

76

2.2

160

2.6

236

2.5

 

  Total

3439

 

6056

 

9495

  

Other co-morbidities

       

  No

2640

81.3

4687

84.0

7327

83.0

0.001

  Yes

608

18.7

896

16.1

1504

17.0

 

  Total

3248

 

5583

 

8831

  

DOT

       

  No

2746

75.9

5390

76.0

8136

75.9

0.954

  Yes

872

24.1

1706

24.0

2578

24.1

 

  Total

3618

 

7096

 

10714

  

HIV status

       

  Negative

1267

74.7

2011

76.7

3278

75.9

0.135

  Positive

430

25.3

614

23.4

1044

24.1

 

  Total

1697

 

2625

 

4322

  

FDC = fixed-dose combination; R = rifampin; H = isoniazid; Z = pyrazinamide; E = ethambutol, DOT = directly observed treatment.

Regarding health service characteristics, patients receiving RHZE-FDC were more likely to be treated in units treating less than 125 cases per year, with DOT implemented, performing follow-up smears and having exclusively primary care services. Conversely, those receiving RH-FDC + Z were more likely to have complete health teams, a social service, community health agents, the Family Health Strategy, teaching activities and primary care (Table 3).
Table 3

Characteristics of health care units where pulmonary tuberculosis patients were treated according to the type of treatment from October 2009 to September 2010

Characteristics

FDC-RHZE

RH-FDC + Z

Total

p-value

 

N

%

N

%

N

%

 

The unit assists over 125 cases yearly

    

  No

1989

53.2

3574

48.5

5563

50.1

0.000

  Yes

1748

46.8

3800

51.5

5548

49.9

 

  Total

3737

 

7374

 

11111

  

The unit offers DOT

      

  No

440

11.8

1621

22.0

2061

18.6

0.000

  Yes

3297

88.2

5753

78.0

905

81.5

 

  Total

3737

 

7374

 

11111

  

The unit requests follow up smears

   

  No

283

7.6

2135

29.0

2418

21.8

0.000

  Yes

3454

92.4

5239

71.1

8693

78.2

 

  Total

3737

 

7374

 

11111

  

The unit has a laboratory facility

    

  No

2477

66.3

4763

64.6

7240

65.2

0.070

  Yes

1260

33.7

2611

35.4

3871

34.8

 

  Total

3737

 

7374

 

11111

  

The unit has a complete team with physician, nurse and social worker

 

  No

2153

57.6

1872

25.4

4025

36.2

0.000

  Yes

1584

42.4

5502

74.6

7086

63.8

 

  Total

3737

 

7374

 

11111

  

The unit has a Social Service

     

  No

2153

57.6

1872

25.4

4025

36.2

0.000

  Yes

1584

42.4

5502

74.6

7086

63.8

 

  Total

3737

 

7374

 

11111

  

The unit has community health agents

    

  No

2626

70.3

2980

40.4

5606

50.5

0.000

  Yes

1111

29.7

4394

59.6

5505

49.6

 

  Total

3737

 

7374

 

11111

  

The unit has the Family Health Program

   

  No

2664

71.3

3573

48.5

6237

56.1

0.000

  Yes

1073

28.7

3801

51.6

4874

43.9

 

  Total

3737

 

7374

 

11111

  

The unit has training activities

    

  No

3534

94.6

6249

84.7

9783

88.1

0.000

  Yes

203

5.4

1125

15.3

1328

12.0

 

  Total

3737

 

7374

 

11111

  

The unit has primary care

     

  No

2692

72.0

2205

29.9

4897

44.1

0.000

  Yes

1045

28.0

5169

70.1

6214

55.9

 

  Total

3737

 

7374

 

11111

  

The unit has exclusively primary care

   

  No

2832

75.8

6543

88.7

9375

84.4

0.000

  Yes

905

24.2

831

11.3

1736

15.6

 

  Total

3737

 

7374

 

11111

  

FDC = fixed-dose combination; R = rifampin; H = isoniazid; Z = pyrazinamide; E = ethambutol, DOT = directly observed treatment.

The effect of FDC-RHZE on treatment default

In the present study period, in the five cities, default was the treatment outcome in 14% of new cases. This rate varied from 7.5% in Salvador to 20.3% in Porto Alegre. The FDC-RHZE regimen appears to have a protective effect against default compared to the RH-FDC + Z regimen but this lost significance when adjusted for individual characteristics. Older age and higher education occupation had a protective effect while alcoholism and HIV co-infection were directly associated to defaulting (Additional file 1: Table S1).

When health clinic characteristics are considered, the FDC-RHZE regimen has a protective effect, even when adjusted for the characteristics that influence default. The existence of a laboratory facility in the health unit was the most important characteristic protecting against default. Other protective characteristics were DOT adoption and follow-up smears (Additional file 1: Table S2).

The final hierarchized model including both individual and health facility characteristics showed that the FDC-RHZE has a 14% protective effect against default, detectable when excluded the influence of the other aspects that are also associated with default (Table 4).
Table 4

Risk factors for TREATMENT DEFAULT among pulmonary tuberculosis patients from October 2009 to September 2010 (hierarchized model)

Characteristics

%

OR

95% CI

adjOR

95% CI

FDC-RHZE

     

  No

66.4

1

 

1

 

  Yes

33.6

0.811

0.723 - 0.910

0.862

0.523 - 0.998

Age

     

  <38 years

54.4

1

 

1

 

  ≥38 years

45.5

0.620

0.555 - 0.692

0.599

0.484 - 0.742

Higher education occupation

     

  No

97.0

1

 

1

 

  Yes

3.0

0.355

0.217 - 0.582

0.223

0.081 - 0.610

Alcohol use

     

  No

81.8

1

 

1

 

  Yes

18.2

1.555

1.349 - 1.793

1.767

1.377 - 2.268

The unit offers DOT

    

  No

18.5

1

 

1

 

  Yes

81.5

0.946

0.826 - 1.082

0.979

0.850 - 1.128

The unit requests follow up smears

  

  No

21.7

1

 

1

 

  Yes

78.3

0.914

0.805 - 1.037

0.947

0.826 - 1.087

The unit has a laboratory facility

  

  No

65.2

1

 

1

 

  Yes

34.8

0.904

0.808 - 1.012

0.892

0.796 - 1.001

Bold numbers are statistically significant findings. FDC = fixed-dose combination; R = rifampin; H = isoniazid; Z = pyrazinamide; E = ethambutol, DOT = directly observed treatment; OR = odds ratio; adjOR = adjusted odds ration; CI = confidence interval.

The effect of FDC-RHZE on negativation of second month follow-up smears

The information on follow up smear at the second month was available for 2,792 (25.1%) patients. Negativation of second month smear occurred in 68% of them. The highest rate of negativation was observed in Manaus (74%) and the lowest in Rio de Janeiro (56%).

Compared to those using RH-FDC + Z, patients receiving FDC-RHZE had a higher probability of having a negative smear on the second month of treatment. The individual characteristics influence little this outcome, a part from a using DOT (Additional file 1: Table S3).

However, when simultaneously considering the health facility-related characteristics, the protection by FDC-RHZE is not sustained. Patients treated in units with more than 125 cases yearly are less likely to have a negative smear on the second month, while the inverse is observed among those treated in units that adopted DOT or have exclusively primary care services (Additional file 1: Table S4).

The final, hierarchized model shows that FDC-RHZE has no influence on the second month-smear negativation. The other variables with an influence in the specific model sustained significance in the final model (Table 5).
Table 5

Risk factors for SECOND MONTH SMEAR NEGATIVATION among pulmonary tuberculosis patients from October 2009 to September 2010 (hierarchized model)

Characteristics

%

OR

95%CI

adjOR

95%CI

FDC-RHZE

     

  No

66.4

1

 

1

 

  Yes

33.6

1.104

0.932 - 1.307

1.164

0.999 - 1.372

DOT

     

  No

75.9

1

 

1

 

  Yes

24.1

1.450

1.208 - 1.739

1.373

1.137 - 1.658

The unit assists over 125 cases yearly

  

  No

50.1

1

 

1

 

  Yes

49.9

0.782

0.663 - 0.922

0.817

0.686 - 0.974

The unit has exclusively primary care

  

  No

84.4

1

 

1

 

  Yes

15.6

1.289

1.065 - 1.559

1.336

1.099 - 2.126

Bold numbers are statistically significant findings. FDC = fixed-dose combination; R = rifampin; H = isoniazid; Z = pyrazinamide; E = ethambutol, DOT = directly observed treatment; OR = odds ratio; adjOR = adjusted odds ration; CI = confidence interval.

Discussion

In the present study, default rate was high (14%), significantly higher than the rate tolerated by WHO (5%) [13]. This is not a surprise, given the default rates reported in the country as a whole [3]. Our analysis showed that as compared to RH-FDC + Z, RHZE-FDC had a protective effect of 14% against defaulting from tuberculosis treatment. However, no protective effect was observed for second month-smear negativation.

Studies comparing FDC and separated drug outcomes using secondary notification data were not found in the literature. However, the set of controlled trials in the last two decades that analysed FDC versus single drugs for tuberculosis treatment found no protective effects on cure, relapse or smear negativation rates [11]. However, programmatic, operational studies can have different outcomes when compared with the controlled conditions of a randomized controlled trial. In our evaluation using the MoH database, previously shown to be suitable for this type of analyses, we did not find such protection either, at least when compared to RH-FDC + Z. The outcome default using FDCs has been less explored in the literature. Both older (1987) [14] and more recent (2002) [15] studies did not detect any difference in default rates, although smear negativation rates increased with FDC in the former, as well as in more recent studies [16].

The most important experimental study on this matter was recently published by Lienhardt et al. [17]. This randomized controlled trial known as The Study C was conducted in 11 sites in Africa, Asia and Latin America between 2003 and 2008. Unlike ours, this study aimed to evaluate safety and effectiveness of FDC-RHZE compared to RHZE in separate formulation, and the main outcome was a negative culture at 18 months after treatment onset. The study concluded that the non-inferiority condition was attained and that FDCs are better accepted because of the potential advantages associated with their administration as compared to the separate drugs. Unlike the previously reported studies, ours uses an observational methodology, and two different regimens (not only the formulation) are compared. Thus, we cannot conclude that the benefits of the RHZE-FDC regimen are due exclusively to its fixed-dose presentation, since doses were different and an additional drug (E) was included.

Because randomization is not possible in the used study design, we adjusted for potential confounding variables, both at the individual and at the health service level. Our results indicate that at the individual level, besides the regimen, patients with older age and higher education occupation, a proxy for socioeconomic status, were less likely to default, while alcoholism increased the risk for default. These individual variables were largely explored in the literature and there is solid evidence to support their role in defaulting, as summarized in a meta-analysis [18,19]. Other characteristics not present in SINAN database, such as adverse events and unemployment, and other not amenable in this king of study, such as knowledge and believes, have also been shown to influence default rates [18,19] It is beyond of the scope of the present study to discuss each of these factors. They were only analysed to verify if the effect of the RHZE-FDC regimen was spurious or independent of these variables, since there was no randomization. Likewise, although drug bioavailability is another important factor explored in FDC studies, this discussion is out of the scope of the present analysis [20,21]. Finally, regarding the laboratory outcome, negative culture at 18 months, recommended as an endpoint by international bodies to evaluate failure and relapse, was not available in the Brazilian surveillance database. Second-month negativation is indeed, not a sensitive surrogate for these outcomes. Our choice of the second-month negativation as an outcome was however justified because [1] it was the best available information, since it is a national recommendation to request culture if the mandatory sputum smear at the second month is positive and [2] the rationale for the regimen replacement was high rates of default and of resistance, and the second-month negativation is a good predictor of resistance.

Adherence is probably the factor that most influence the effectiveness of any treatment [22]. This is the reason why we chose default as one of the outcomes in the present analysis. Besides influencing effectiveness, irregular and incomplete tuberculosis treatments are also responsible for emergence of multidrug resistant-tuberculosis (which we could not evaluate).

Interestingly, while only individual characteristics and the FDC regimen had an effect on default, only health care characteristics, such as DOT, service organization and workload influenced the smear negativation rate. The Family Health Strategy increases the bonding between the community and the health services [5]. This attachment, mostly developed through the community health agent, may be at the origin of better tuberculosis treatment outcomes in Brazil [19,23]. Likewise, despite the controversy [24,25], DOT has been recognized as an excellent strategy that has prevented 4.6–6.3 million deaths between 1995 and 2009 in the world since its implementation [26]. Finally, the importance of a multidisciplinary team to deal with this socially determined disease could not be overemphasized.

Individual characteristics presented by patients from our sample might have been a result of selection bias. However, they had the same profile as those not included in the analyses (data not shown) thus we do not believe our results are a consequence of bias. Another possible limitation would be the quality of data itself, since the source of the database was the routine surveillance information system. Nevertheless, a previous quality control [12] showed that the data gathered was adequate for analysis. The sputum negativation outcome was available only for one quarter of patients, reducing the statistical power for this outcome. However, it is unlikely that it jeopardizes the validity of the results. In addition, despite selecting new cases, multiresistant cases could have been included, but again, it is unlikely that those patients could have selectively received one of the treatment regimens. Finally, a classification bias might have occurred because we considered any RHZE as using FDC formulation in the period of the intervention. Although this can have overestimated the number of patients under FDC, it is unlikely that it had any effect on the analysis of individual and collective factors associated with the selected outcomes.

On the other hand, the inclusion of several cities with heterogeneous health unit performance and different probabilities of use of the treatment regimens allowed a wide spectrum of individual and health system characteristics, necessary for adjustments of the effect measures. For example, most patients in Rio received the RH-FDC + Z regimen in heterogeneous health units. This is the reason why we adjusted for health unit characteristics and not for cities. In addition, the option of conducting a study with an internal comparison group instead of a “before and after” design reduces the chances of observing effects (such as default rates) that could be attributed to other non-controlled interventions concurrent to the implementation of the new regimen.

Although observational studies are not ideal for evaluating programmatic interventions, this was the only possible method because the intervention was already launched when we planned the study. On the other hand, it had the advantage of showing the pragmatic effect of the “new” treatment on notified cases. Retrospectively, it strengthens the Brazilian NTP decision to change the treatment in the country. As new, shorter regimens are under investigation and expected for a near future (as pointed at http://www.tballiance.org/downloads/Pipeline/TBA%20Pipeline%20Q1%202015%282%29.pdf), it is important to plan cluster randomized studies to evaluate the effectiveness of the intervention at the health service level. However, secondary data from the national surveillance system is also a source of reliable and useful information in early adopter countries.

Conclusions

In summary, our analysis of a cohort database in a high burden country shows that compared to RH-FDC + Z, RHZE-FDC reduces the default rates by 14%, independently of other influencing individual or health service factors, which eventually have a stronger effect.

Declarations

Acknowledgements

Supported by the Ataulpho de Paiva Foundation, through a grant (OPGH 5254) by the Bill and Melinda Gates Foundation. AT has a research grant by CNPq. We acknowledge Draurio Barreira, coordinator of the Brazilian NTP for allowing access to the tuberculosis database. None of the mentioned funding agencies are responsible for the statements in this article.

Authors’ Affiliations

(1)
National School of Public Health, Fiocruz
(2)
Social Medicine Institute, Rio de Janeiro State University
(3)
Federal University of Rio de Janeiro
(4)
Montreal Chest Institute, McGill University

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