Background
In a large randomized trial, Utrecht PROactive Frailty Intervention Trial (U‐PROFIT), we evaluated the effectiveness of an integrated program on the preservation of daily functioning in older people in primary care that consisted of a frailty identification tool and a multicomponent nurse‐led care program. Examination of treatment fidelity is critical to successful translation of evidence‐based interventions into practice.

Aims
To assess treatment delivery, dose and content of nursing care delivered within the nurse‐led care program, and to explore if the delivery may have influenced the trial results.

Methods
A mixed‐methods study was conducted. Type and dose of nursing care were collected during the trial. Shortly after the trial, a focus group with nurses was conducted to explore reasons for the observed differences between the type and dose of nursing care delivered.

Results
A total of 835 older persons were included in the nurse‐led care program. The mean age was 75 years, 64% were female and 53.5% were living alone. The most frequent self‐reported conditions were loneliness (60.8%) and cognitive problems (59.4%). One‐third of the patients with a geriatric condition received an additional assessment (e.g., Mini‐Mental State Examination), and the majority of these patients received at least one nurse intervention (>85%). Most nursing care was delivered to patients at risk of falling and to those with urinary incontinence. Patients with nutrition problems seldom received nursing interventions. The nurses explained that differences in type and dose were influenced by the preference of the patient, the type of geriatric problem, and the time required to apply a nurse intervention.

Linking Evidence to Action
All intervention components were delivered; however, differences were observed in the type and dose of nursing care delivered across geriatric conditions. The findings better explain the treatment fidelity and suggest that there is room for improvement that may result in more beneficial patient outcomes.