Stewardship / Resistance Scan for Feb 08, 2019

Inadequate TB drug-susceptibility testing
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New UK guidance on antibiotics for acute cough

Study: Inadequate drug-susceptibility tests linked to poor TB treatment

The accuracy of tuberculosis (TB) drug-susceptibility testing in high-burden countries was inadequate, and inaccurate test results led to inadequate treatment that contributed to higher mortality in patients with drug-resistant forms of the disease, an international team of researchers reported yesterday in The Lancet Infectious Diseases.

In a multicenter cohort study conducted in seven high-burden countries (Cote d'Ivoire, Democratic Republic of the Congo, Kenya, Nigeria, South Africa, Peru, and Thailand), researchers collected tuberculosis isolates from patients aged 16 years and older and compared the results of drug-susceptibility testing done locally with results from gold-standard phenotypic drug-susceptibility testing conducted in a Swiss reference laboratory. They then examined mortality in patients who had concordant and discordant test results.

Drug-susceptibility tests of isolates from 634 patients at the reference lab found that 394 isolates (62%) were pan-susceptible, 45 (7%) were resistant to one drug, 163 (26%) were multidrug-resistant (MDR), and 30 (5%) were pre-extensively or extensively drug-resistant (pre-XDR or XDR). A comparison of the results from the local and reference laboratories showed that they were concordant for 513 (81%) of 634 patients and discordant for 121 (19%) of 634, resulting in an overall sensitivity of 90.8% (95% confidence interval [CI], 86.5 to 94.2) and specificity of 84.3% (95% CI, 80.3 to 87.7).

Mortality ranged from 6% (20 of 336) in patients with pan-susceptible strains and concordant test results who were treated according to World Health Organization (WHO) guidelines to 57% (8 of 14) in patients with resistant strains who were under-treated. More than half the people with misdiagnosed drug-resistant tuberculosis who received inadequate therapy died. In logistic regression models, compared with concordant drug-susceptibility test results, the adjusted odds ratio of death was 7.33 (95% CI, 2.70 to 19.95) for patients with discordant results who were under-treated.

The authors of the study say the results support the idea that rapid molecular drug-susceptibility testing at treatment initiation, preferably using whole-genome sequencing, is required to improve outcomes in patients with MDR and pre-XDR/XDR TB, though they acknowledge that much work is required to make that approach feasible and affordable in lower-income countries.

They conclude, "In the meantime, the capacity for the phenotypic and molecular drug-susceptibility testing recommended by WHO should be increased to ensure the most adequate treatment of drug-resistant tuberculosis in these settings."
Feb 7 Lancet Infect Dis study

 

UK releases new guidance on antibiotic prescribing for acute cough

The UK National Institute for Health and Care Excellence (NICE) yesterday issued new clinical guidance aimed at reducing antibiotic prescribing for adults and children with acute cough.

The guidance advises against offering antibiotics to treat patients with acute cough associated with either an upper respiratory tract infection or with acute bronchitis who are not systematically unwell. Clinicians are also advised to explain to patients why an antibiotic is not necessary, how long acute coughs lasts, how to manage symptoms with self-care (honey, herbal remedies, and over-the-counter cough medicine), and when to seek further medical help.

For patients who appear systematically unwell at a face-to-face examination, the guidance recommends an antibiotic be offered immediately. For patients with a higher risk of complications, the guidance suggests clinicians consider offering an antibiotic.

The guidance recommends doxycycline as the first-choice antibiotic for adult patients, and amoxicillin as the first-choice agent in children under the age of 18.
Feb 7 UK NICE acute cough guidance

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