Medical care providers have very limited knowledge of resistance-associated drug mutations

Graham McKerrow HIV i-Base

A study of New York medical care providers attending an AIDS conference found they had “markedly limited” knowledge of resistance-associated drug mutations and that most incorrectly interpret test results.

The majority of providers questioned used interpretations provided by laboratories and few said they used guidance from recognised experts in resistance testing.

Researchers from the Elmhurst Hospital Centre and the Mount Sinai School of Medicine, New York, distributed an anonymous questionnaire at a meeting for HIV care providers organised by the International AIDS Society-USA in 2001.

The 100 providers who used genotypic testing and returned the questionnaires include 23 nurse practitioners and physician’s assistants and 77 physicians. They were given a list of six drug groups and a list of 16 resistance-associated point mutations and were asked to write next to each drug group the point mutations associated with resistance to that drug.

The results show that 17% of respondents correctly identified at least one resistance mutation for each of six drug groups, whereas 3%, 4%, 10%, 16% and 14% correctly identified resistance mutations for 5, 4, 3, 2 and 1 drug group respectively.

Thirty-six per cent of providers were unable to correctly identify resistance mutations for any of the six drug groups. The average number of drug groups for which providers correctly identified resistance mutations was two.

The researchers report that there was no difference in knowledge among providers on the basis of degree or specialty. Provider patient load was significantly associated with improved knowledge of resistance mutations; those caring for >50 patients were more apt to correctly identify resistance mutations for >or=4 drug groups than were those caring for <or=50 patients (37% vs. 6%; P = .001). Knowledge also was better among self-described experts, with 8 (53%) of 15 having knowledge of resistance mutations for >or=4 drug groups (P = .01).”

In a substudy analysis, the rersearchers found that of the 38 physicians caring for 100 patients or more 12 (32%) could identify resitance mutations for four or more drug groups., and eight (21%) were unable to correctly identify resistance mutations for any of the drug groups.

The researchers write of the substudy group: “Because of their greater patient load, these physicians were considered more likely to be HIV-dedicated clinicians. Despite their greater patient load, they exhibited a similar limited knowledge of resistance mutations, which suggests that our overall results may, in fact, be representative of HIV care providers in general.”

The authors introduce their report by writing: “Resistance to antiretroviral agents is an important challenge facing providers of care to patients with human immunodeficiency virus. Prospective clinical trials have demonstrated improved short-term virologic outcomes when the choice of antiretroviral drugs was aided by genotypic testing, with further improvements seen when interpretations were guided by experts. Major guidelines recommend the use of genotypic testing to guide treatment changes and emphasize the importance of expert interpretation.

“Evaluating genotypic test results is complex, and laboratory-provided interpretations do not follow a universal standard. For proper interpretation, clinicians must have a basic knowledge of relevant resistance-associated genotypic mutations and must recognize the extent to which they affect susceptibility to specific drugs.”

Their Discussion concludes: “These data highlight problems with the current approach to the interpretation of genotypic testing by clinicians. A standardized algorithm of genotype interpretation that is continually updated and used by all laboratories that perform genotypic testing would be valuable. However, providing more education to HIV specialists about genotype interpretation and improving their access to well-defined recognized experts in the field of HIV resistance are most important.”


Salama C, Policar M, Cervera C. Knowledge of genotypic resistance mutations among providers of care to patients with human immunodeficiency virus. Clin Infect Dis 2003 Jan 1;36(1):101-4


This highlights the importance of the expert interpretations that are provided with all resistance tests performed in the UK and the additional consultation expertise provided by the laboratories that run these assays should be utilised.

It is worth re-emphasing that tests, whether genotypically or phenotypically based, only provide an indication of drug sensitivlty to the antiviral agents used in the current or most recent combination. A full indication of drug resistance needs to take into account an individual’s lifetime treatment history and drug exposure.

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