The impact of changing the diagnostic algorithm for TB in Manicaland, Zimbabwe

SETTING

Governmental health facilities performing TB diagnostics in Manicaland, Zimbabwe.

OBJECTIVE

To investigate the effect of making Xpert® MTB/RIF the primary TB diagnostic for all patients presenting with presumptive TB on 1) the number of samples investigated for TB, 2) the proportion testing TB-positive, and 3) the proportion of unsuccessful results over time.

DESIGN

This retrospective study used data from GeneX-pert downloads, laboratory registers and quality assurance reports between 1 January 2017 and 31 December 2018.

RESULTS

The total number of Xpert tests performed in Manicaland increased from 3,967 in the first quarter of 2017 to 7,011 in the last quarter of 2018. Mycobacterium tuberculosis DNA was detected in 4.9-8.6% of the samples investigated using Xpert, with a higher yield in 2017 than in 2018. The overall proportion of unsuccessful Xpert assays due to "no results", errors and invalid results was 6.3%, and highly variable across sites.

CONCLUSION

Roll out of more sensitive TB diagnostics does not necessarily result in an increase of microbiologically confirmed TB diagnosis. While the number of samples tested using Xpert increased, the proportion of TB-positive tests decreased. GeneXpert soft- and hardware infrastructure needs to be strengthened to reduce the rate of unsuccessful assays and therefore, costs and staff time.

Evaluation of OMNIgene®•SPUTUM reagent for mycobacterial culture

SETTING

National Mycobacterium Reference Laboratory, Borstel, Germany.

OBJECTIVE

To evaluate the effectiveness of OMNIgene®•SPUTUM (OM-S) reagent in comparison with a method using N-acetyl-L-cysteine-sodium hydroxide (NALC-NaOH) with regard to mycobacterial recovery and contamination of broth and solid cultures.

DESIGN

Sputum samples from patients with tuberculosis and other respiratory diseases underwent decontamination with NALC-NaOH-based (MycoDDR™) or OM-S reagent. The decontamination procedure was assigned by block randomisation. Samples were inoculated on Löwenstein-Jensen, Stonebrink and MGIT™ (Mycobacterial Growth Indicator Tubes). Mycobacterial recovery from samples spiked with Mycobacterium tuberculosis following decontamination was determined.

RESULTS

Eighty-five samples were randomised to NALC-NaOH and 84 to OM-S reagent. Mycobacterial recovery was significantly lower for samples processed with OM-S reagent compared with the NALC-NaOH method across all media types. Culture contamination was lower with NALC-NaOH reagent on solid media (9.4-12.9% vs. 28.6-29.8%). Growth was not observed in MGIT among samples spiked with 10 600-16 800 colony-forming units of M. tuberculosis following decontamination with OM-S reagent.

CONCLUSION

Low mycobacterial recovery, especially in MGIT, observed in the present study suggests that OM-S reagent might not be compatible with the MGIT system. More extensive field evaluations of the OM-S reagent are warranted to demonstrate a significant benefit over currently used methods.

Treatment responses in multidrug-resistant tuberculosis in Germany

BACKGROUND

Excellent treatment outcomes have recently been reported for patients with multi/extensively drug-resistant tuberculosis (M/XDR-TB) in settings where optimal resources for individualised therapy are available.

OBJECTIVE

To ascertain whether differences remain in treatment responses between patients with M/XDR-TB and those with non-M/XDR-TB.

METHOD

Patients with TB were prospectively enrolled between March 2013 and March 2016 at five hospitals in Germany. Treatment was conducted following current guidelines and individualised on the basis of drug susceptibility testing. Two-month and 6-month sputum smear and sputum culture conversion rates were assessed. A clinical and radiological score were used to assess response to anti-tuberculosis treatment.

RESULTS

Non-M/XDR-TB (n = 29) and M/XDR-TB (n = 46) patients showed similar rates of microbiological conversion: 2-month smear conversion rate, 90% vs. 78%; culture conversion rate, 67% vs. 61%; time to smear conversion, 19 days (IQR 10-32) vs. 31 days (IQR 14-56) (P = 0.066); time to culture conversion, 39 days (IQR 17-67) vs. 39 days (IQR 6-85) (P = 0.191). Both clinical and radiological scores decreased after the introduction of anti-tuberculosis treatment.

CONCLUSION

There were no significant differences in scores between the two groups until 6 months of treatment. Under optimal clinical conditions, with the availability of novel diagnostics and a wide range of therapeutic options for individualised treatment, patients with M/XDR-TB achieved 6-month culture conversion rates that were compatible with those in patients with non-M/XDR-TB.

Impact of quality improvement in tuberculosis laboratories in low- and lower-middle-income countries: a systematic review

BACKGROUND

The effect of quality improvement measures on the performance of diagnostic tuberculosis (TB) laboratories in low- and lower-middle-income countries is not known, and is the subject of this review.

METHODS

Three databases were searched for quality improvement studies presenting data on performance parameters before and after the implementation of quality improvement interventions.

RESULTS

Twenty-one studies were included in this review. Quality improvement measures were most frequently implemented by an external organization; settings targeted ranged from microscopy centers, hospitals, districts, regional and national reference laboratories. Quality improvement interventions and outcome measurements were highly heterogeneous. Most studies investigated interventions aimed at improving smear microscopy (n = 17). Two studies evaluated comprehensive quality improvement measures (n = 2) and another three studies focused on mycobacterial culture and drug susceptibility testing. Most studies showed an improvement in outcomes measured on before-after or time trend analysis.

CONCLUSION

Quality improvement measures implemented in TB laboratories showed a positive impact on various outcomes. Due to the high heterogeneity of outcome reporting and interventions and the low quality of the studies, the effect size was not clear. Identification of standardized quality indicators and their link to the quality of patient care would improve knowledge in this field.

Evaluation of weight-based prescription of antiretroviral therapy in children

Objectives

The aim of the study was to investigate the extent of and factors associated with incorrect dosing of antiretroviral therapy (ART) in HIV‐infected children in Harare, Zimbabwe.

Methods

All children aged 0–10 years and children aged 11–17 years who weighed < 35 kg and taking ART were recruited from the paediatric HIV clinic at Harare Hospital. Their current doses of ART drugs were compared against doses recommended by the national guidelines.

Results

Among 309 children recruited [55% male; median age 7 years (interquartile range (IQR) 5–10 years)], the median CD4 count was 899 cells/μL and the median duration of their current ART regimen was 11.2 months (IQR 4.9–17.1 months). Overall, 110 (35.6%) children were prescribed incorrect doses of at least one drug component within their ART regimen; 64 (20.7%) under‐dosed and 49 (15.9%) over‐dosed on at least one drug. Children receiving a higher than recommended dose of at least one drug were younger compared with correctly dosed children (median 6 versus 7 years, respectively; P = 0.001), had been on their current ART regimen for a shorter time (median 7.2 versus 13 months, respectively; P = 0.003) and were less likely to be receiving a three‐drug fixed‐dose combination (FDC; 42.9 versus 63.3%, respectively; P = 0.009). Those who were under‐dosed were also less likely to be on a three‐drug FDC (25 versus 63.3%, respectively; P < 0.001).

Conclusions

Over a third of children were prescribed incorrect doses of ART. Children taking triple‐drug FDCs were likely to be correctly dosed. Our study highlights the importance of weight monitoring at each clinical contact, training of health care providers on paediatric drug dosing and the need for wider availability of FDCs for children.

Turnaround time of whole genome sequencing for mycobacterial identification and drug susceptibility testing in routine practice

OBJECTIVES

Until recently whole genome sequencing (WGS) for mycobacteria has been restricted mostly to the research setting. However, in 2017 Public Health England has implemented WGS for routine mycobacterial identification and susceptibility testing for Mycobacterium tuberculosis. Our objective was to evaluate the impact of this change on the laboratory turnaround times and availability of results.

METHODS

Over the years 2016 and 2017, the period 1 January to 30 April was selected to represent before and after implementation of WGS. Prior to 2017, line probe assays were used for mycobacterial species identification. Turnaround times for the different steps of the diagnostic process were evaluated for all positive mycobacterial cultures that were sent from our hospital to the Reference Laboratory during the study period.

RESULTS

A total of 161 positive mycobacterial cultures were sent to the Reference Laboratory. Half of the isolates (n=81/161, 50%) were M. tuberculosis and 80/161 (50%) were non-tuberculous mycobacteria. The median number of workdays for mycobacterial species identification was 1 day (interquartile range (IQR) 1-3) in 2016 and 6 days (IQR 5-7) in 2017, p <0.001. For M. tuberculosis complex, the median time to drug susceptibility testing results, either molecular or phenotypic, was 12 days (IQR 11-18) in 2016 and 8 days (IQR 7-10) in 2017, p <0.001.

CONCLUSIONS

Routine WGS performed well in this setting for mycobacterial identification and susceptibility testing for M. tuberculosis and decreased time to drug susceptibility testing results. There was an increase in turnaround times for species identification using WGS, when compared with the previous methods.

Ascertaining in vivo virulence of Mycobacterium tuberculosis lineages in patients in Mbeya, Tanzania

We evaluated the relationship between the degree of immunodeficiency indicated by the number of circulating CD4+ T-cells and Mycobacterium tuberculosis lineages identified by spoligotyping and mycobacterial interspersed repetitive units-variable number of tandem repeats genotyping in human immunodeficiency virus (HIV) infected individuals with pulmonary tuberculosis from Mbeya, Tanzania. Of M. tuberculosis strains from 129 patients, respectively 55 (42.6%) and 37 (28.7%) belonged to Latin American Mediterranean and Delhi/Central-Asian lineages, while 37 (28.7%) patients were infected with other strains. There was no difference in the distribution of M. tuberculosis lineages among patients with early or advanced stages of HIV infection (P = 0.785), indicating that the virulence of strains from these lineages may not be substantially different in vivo.