New Guideline for Cumulative Antimicrobial Susceptibility Test Data

Susceptibility statistical data, consisting of the cumulative and ongoing summary of the patterns of antimicrobial susceptibility of clinically important microorganisms, are important to the practice of medicine. The Clinical and Laboratory Standards Institute (CLSI) announces it has updated the document, “Analysis and Presentation of Cumulative Antimicrobial Susceptibility Test Data; Approved Guideline—Third Edition” (M39-A3). The primary aim of the document is to provide a guide for the preparation of cumulative antimicrobial susceptibility test data reports that will prove useful to clinicians in the selection of the most appropriate agents for initial empirical antimicrobial therapy.

Rebecca T. Horvat, PhD, D (ABMM), director of clinical microbiology at the University of Kansas Hospital and associate professor of pathology and lab medicine at the University of Kansas Medical Center in Kansas City, Kan., says, “Antimicrobial resistance continues to increase in clinical pathogens. Monitoring these changes and making a determination of significant developments can be challenging. A rationale approach to monitoring new resistance patterns allows health care institutions to develop reasonable protocols to identify changes that affect treatment option. The new, approved CLSI document M39-A3 continues to give some clear advice and ideas on calculating and presenting antimicrobial susceptibility data.”

Elizabeth Palavecino, MD, director of clinical microbiology at Wake ForestUniversity Baptist Medical Center, agrees: “M39 provides wonderful guidance to clinical laboratories in the preparation of cumulative antibiograms. The document provides very useful algorithms for handling repeat isolates to avoid reporting misleading information. The recommendations for the analysis and presentation of data are practical and clinically relevant.”

This document is a revision of M39-A2, which was published in 2005, and includes the following updates:

-- Added various options for presenting data when the incidence of a specific multidrug-resistant organism is significant in a facility.

-- Expanded recommendations for calculating percent susceptible for subsets of isolates (e.g., specific wards, patient types, and body sites).

-- Added recommendations for calculating the percentage of isolates susceptible to either or both of two antimicrobial agents that might be considered for combination therapy.

The recommendations in M39-A3 are intended to be used by individuals involved in the following:

-- analyzing and presenting antimicrobial susceptibility test data (e.g., clinical microbiologists, pharmacists, physicians)

-- utilizing cumulative antimicrobial susceptibility test data to make clinical decisions (e.g., clinical microbiologists, infectious disease specialists and other clinicians, infection control practitioners, pharmacists, epidemiologists, other healthcare personnel, and public health officials)

-- designing information systems for the storage and analysis of antimicrobial susceptibility test data (e.g., laboratory information system vendors, manufacturers of diagnostic products that include epidemiology software packages)

For additional information, visit the CLSI Web site at www.clsi.org.

CLSI, formerly NCCLS, is a global, nonprofit, membership-based organization dedicated to developing standards and guidelines for the healthcare and medical testing community. CLSI’s unique consensus process facilitates the creation of standards and guidelines that are reliable, practical, and achievable for an effective quality system