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Table 4 The COS use in trials aimed at improving AMS in care homes and recommended OMIs

From: Development of a core outcome set for clinical trials aimed at improving antimicrobial stewardship in care homes

Outcome Outcome definition Recommended OMI
Delivery of care
The total number of antimicrobial courses prescribed
(Main outcome)
The total number of antimicrobial courses that are prescribed for care home residents over a period of time (e.g. over a month, or a year) This outcome should be measured by the OMI ‘Incidence of antimicrobial use’. This OMI is defined as the number of antibiotic courses started per 1000 resident-days. This can be calculated by the following formula:
(Number of antimicrobial courses started / number of resident-days) × 1000
 + An antimicrobial course started is defined as all antimicrobials given continuously for one particular indication. This is deemed to be one course (including antimicrobial switch or extension of treatment duration). Antimicrobials prescribed for a second indication during the same period or prescribed after an antimicrobial-free duration of seven days for the same indication is deemed to be a separate course. In the case that treatment documentation cannot be identified, prescription date and treatment duration can be used to deduce an antimicrobial course. An antimicrobial-free duration of seven days can be applied to identify a new course
 + A resident day is defined as each date of service in which a care home resident was present in the facility and received services
Days of therapy per 1000 resident-days
(Optional outcome)
The duration (in days) of antimicrobial courses that are prescribed for care home residents, standardised to 1000 resident-days This outcome should be measured by the OMI ‘Rate of antimicrobial days of therapy per 1000 resident-days’. This OMI can be calculated by the following formula:
(Number of antimicrobial days of therapy / Number of resident-days) × 1000
 + An antimicrobial day of therapy is defined as each day a care home resident is administered a systemic antimicrobial agent
 + A resident day is defined as each date of service in which a care home resident was present in the facility and received services
 + It is noted that this OMI should be applied separately for antimicrobials for TREATMENT of infection and PREVENTION of infection (infection prophylaxis)
Appropriateness of antimicrobial prescribing
(Main outcome)
Antimicrobial courses that are prescribed in accordance with the best available evidence and are suitable for a patient, taking their medical history and medical conditions (including infection) into consideration OMI not available
Mortality/survival
Mortality related to infection
(Optional outcome)
The number of deaths of care home residents related to infection OMI not available
Infection
Rate of antimicrobial resistance
(Optional outcome)
The number of cases in which antimicrobial-resistant bacteria are identified OMI not available
  1. OMI outcome measurement instrument