Characteristics and treatment outcomes of patients with multi-drug resistant tuberculosis at a tertiary care hospital in Peshawar, Pakistan

Study design and settings

Due to an increase in the incidence of DR-TB in Pakistan, patients are treated through Programmatic Management of Drug Resistant TB (PMDT). Different PMDT sites are functional in the country; Lady Reading Hospital Peshawar (LRH), Pakistan is one of most sophisticated health care setup in the Khyber Pakhtunkhwa Province. By utilizing its own resources, the LRH provided support for MDR patients between 2008 and 2012. In 2012 the National TB Control Programme declared the hospital as its PMDT site.

This retrospective cohort study was conducted at PMDT-LRH Peshawar, Pakistan. All confirmed pulmonary MDR-TB patients who were consecutively enrolled for treatment at the study site between January 2012 and December 2012 were included in the study. All the enrolled patients were treated on an ambulatory based care model and were properly examined by a team of clinicians on a monthly basis. All registered patients were initially started on a standardized treatment regimen, and then shifted to individualized regimens according to individual drug susceptibility test results.

Sputum smear, culture, and chest radiographs (CXR) were obtained at the time of enrollment, and then monthly during the intensive phase of treatment, whereas the continuation phase was accompanied by monthly smear and bimonthly culture and chest radiograph. All patients were tested at baseline for HIV, and blood investigations were performed at baseline, and at every month as per national DR-TB guidelines. Patients’ compliance and medication adherence was closely monitored by trained treatment supporters and directly observed therapy facilitators. All patients were psychologically assessed, and personalized counseling was provided on monthly follow up visits. Home visits were arranged for individual patient for contact screening, infection control measures at home and to create a liaison with the regional district TB officer. Adverse events if any, associated with second line drugs were monitored and managed promptly, utilizing multiple approaches of counselling, administering ancillary drugs and in rare cases, permanent removal of any culprit drug from the treatment regimen as a last resort. Patients received counseling to maximize adherence, nutritional support, and transportation reimbursement for their ambulatory visits.

Regimen design and patient management

All the registered patients were started on a standardized/empiric treatment regimen (ETR). The ETR was comprised of pyrazinamide, levofloxacin, ethionamide, cycloserine, and amikacin. The dose was individualized according to weight and clinical condition of each patient as per guidelines of the National TB Control Programme. Treatment on ETR was carried out until the results of drug susceptibility testing (DST). After confirmation of the resistance pattern determined through DST, all patients were shifted to an individualized treatment regimen (ITR) based on the DST profile for an individual patient.8 In general, regimens contained at least 5 drugs on which the infecting strain was susceptible, including a second-line injectable drug for at least 6 months after documented sputum culture conversion. Total treatment duration included a minimum of 12-18 months of post-culture conversion, which was regularly pursued afterwards by Mycobacterium tuberculosis (M. tuberculosis) smears and cultures up to the end of treatment.

Bacteriologic studies and drug susceptibility testing. Specimen processing

All samples were decontaminated with N-acetyl-L-cysteine (NALC) sodium hydroxide according to the standard protocol. All specimens were concentrated by centrifugation for 30 min and sediments were used for acid-fast bacilli microscopy and culture.

Microscopy

Smears for microscopy were screened using auramine-rhodamine staining. Positive slides were further confirmed by staining with Kinyoun modification of Ziehl-Neelsen stain.

Isolation of M. tuberculosis

Mycobacterial cultures were performed on both liquid and solid media. Sediments were cultured at 37°C using Lowenstein-Jensen (LJ) medium and the mycobacteria growth indicator tube (MGIT) (Becton Dickinson Diagnostic Instruments Systems, Sparks, MD, USA). For the LJ slant, 0.1 ml of concentrated specimen was inoculated and incubated for 8 weeks. Mycobacteria growth indicator tube vials were inoculated with 0.5 ml of specimen and incubated at 37°C after supplementation of the medium with oleic acid-albumin-dextrose-catalase and PANTA (Polymyxin B, Amphotericin B, Nalidixic Acid, Trimetho-Prim and Azlocillin). Growth from the positive LJ slant and MGIT vials were first stained with Kinyoun. Mycobacterium tuberculosis was then identified using the Bactec Nap TB differentiation test (Becton Dickinson, Sparks, MD, USA).

Drug susceptibility testing

Drug susceptibility testing was performed using the standard agar proportion method on enriched Middlebrook 7H10 medium (Becton Dickinson, Sparks, MD, USA) at the following drug concentrations: rifampicin (RMP) 1 g/ml and 5 g/ml, isoniazid (INH) 0.2 µg/ml and 1 µg/ml, streptomycin (SM) 2 µg/ml and 10 µg/ml, and ethambutol (EMB) 5 µg/ml and 10 µg/ml.8,9 To ensure the selection of high-level resistance strains for the purposes of this paper, only the higher concentrations were reported. Disc elution susceptibility plates were prepared using paper susceptibility discs (Becton Dickinson, Sparks, MD, USA). McFarland No. 1 the standard suspension of isolates was made from growth on LJ slant and diluted to 10² and 10⁴. The inoculated plates were incubated at 35°C and examined for growth each week for 8 weeks. Mycobacterium tuberculosis was considered resistant to a given drug when growth of 1% above the drug-free control was observed in the drug-containing area. Pyrazinamide (PZA) sensitivity was carried out using Bactec 7H12 medium pH 6.0 at 100 µg/ml (Bactec PZA test medium, Becton Dickinson, Sparks, MD, USA) in accordance with the manufacturer’s instructions. Mycobacterium tuberculosis H37Rv was used as a control with each batch of DST.

Data collection and analysis

Both paper-based as well as electronic documentation were used for efficient and proper utilization of data. Parameters included in documentation were patients’ demographics and their clinical and microbiological data. Demographics data included gender, age, weight, co-morbidities, area of residence, and close contacts. Clinical data included history and outcome of previous TB treatment, previous medication history of any second line drugs and radiological findings at baseline chest x-ray. Microbiological data was composed of baseline sputum smear grading, DST result, and monthly microbiological culture status.

All the data was analyzed using the Statistical Package for Social Sciences version 16.0 (SPSS Inc., Chicago, IL, USA). Comparisons of demographics, socioeconomic status, HIV findings and TB-related characteristics, as well as treatment outcome parameters between patient subgroups were calculated using the Chi-squared test to find out any association between categorical variables, and the Mann-Whitney U-test was used for continuous variables. To estimate the predictors of poor treatment outcome, multivariate logistic regression analysis with Wald statistical criteria using the backward elimination method was performed. All the factors considered in the univariate analysis were entered into the multivariate analysis. P<0.05 was considered statistically significant. The study was approved by the Research and Ethics Committee of the Postgraduate Medical Institute, Peshawar, Pakistan.

Treatment outcomes were defined according to the recommendations from the WHO MDR-TB working group.1 Cured was defined as “treatment completed as recommended by the national policy (minimum 18 months past culture conversion) without evidence of failure and 5 consecutive cultures taken at least 30 days apart, are negative after the intensive phase. If only one positive culture is reported during that time, and there is no concomitant clinical evidence of deterioration, the patient may still be considered cured provided that this positive culture is followed by a minimum of 3 consecutive negative cultures taken at least 30 days apart”.

Treatment failure was defined as “Treatment terminated or need for permanent regimen change of at least 2 anti-TB drugs due to: a) lack of conversion by the end of the intensive phase, or b) bacteriological reversion in the continuation phase after conversion to negative, or c) evidence of additional acquired resistance to fluoroquinolones or second-line injectable drugs, or d) adverse drug reactions (ADRs)”.

Default means an interruption of >2 consecutive months of treatment. Patients were recorded as dead if they died during treatment, regardless of the cause. The XDR-TB is “resistance to any fluoroquinolone and to at least one of 3 second-line injectable drugs (capreomycin, kanamycin and amikacin), in addition to multidrug resistance”. Serious adverse events were defined as those that resulted in any change to the anti-TB drug regimen, either changing the dose of a drug, or temporarily or permanently removing a drug from the regimen. Culture is considered to have converted to negative when 2 consecutive cultures, taken at least 30 days apart, are found to be negative. In such a case, the specimen collection date of the first negative culture is used as the date of conversion.