[LabUpdates] Laboratory Formulary Committee Updates - Antimicrobial susceptibility interpretation - Susceptible-dose dependent

[Matthew Elkins]

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Medicine and laboratory testing are constantly changing. In an attempt to keep us all on the same page, the Laboratory Formulary Committee will be regularly sending out emails with recent updates and guidances. Below are the short versions of relevant changes.


Antimicrobial susceptibility interpretation - Susceptible-dose dependent (SDD):  The SDD interpretive category is relatively new and was created by the Clinical and Laboratory Standards Institute (CLSI) to replace the Intermediate interpretation category for select organism-antimicrobial combinations. This interpretive category is intended to highlight the need to maximize dosing to achieve antimicrobial levels that are likely to be clinically effective.

In our laboratory, the SDD interpretation has been used for daptomycin vs. vancomycin-resistant enterococci (VRE), fluconazole vs. Candida glabrata, and ceftaroline vs. Staphylococcus aureus.

Beginning July 13, 2022, Microbiology will implement updated interpretive breakpoints, including the SDD category, for piperacillin-tazobactam when testing common enteric Gram-negative rods. Susceptibility reports with the SDD interpretation will also include the following result comment:

"Treatment success is more likely when higher and/or more frequent dosing is used, and if the infection is at a site where the antimicrobial concentrates. Consultation with an infectious diseases pharmacist or physician is highly recommended."

See example report below:
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For prior guidances, please visit https://urldefense.com/v3/__https://upstate0.sharepoint.com/sites/LaboratoryFormularyCommitteeLabchanges__;!!GobTDDpD7A!OPMSfY9y68w5LVMvc2x5niVtl-2xWTePR1FaZ0oQJmPK05Ys_8pc0TO6-CkNdibCdgsKntXwIaILL8X83fdo_IcfoOix$ <https://urldefense.com/v3/__https:/upstate0.sharepoint.com/sites/LaboratoryFormularyCommitteeLabchanges__;!!GobTDDpD7A!fMqwKEI3JlieL_eF-Vo4vMVj2PNzfXcL0GsxYMLCbL6cXpbRqzmyQKWIxbV1BBgJ8OlmOsFv$>

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