Study settings

The study was conducted at the WWRC, at HMC [17]. In WWRC, clinical pharmacists are the healthcare providers concerned with performing pharmacotherapeutic follow ups with patients. This is usually achieved through reviewing patients’ charts and suggesting modifications to treatments as necessary. All clinical pharmacists are required to document clinical interventions as they are considered official proof of clinical pharmacists’ efforts to detect and resolve DRPs. A clinical intervention can be initiated by staff/operational (non-clinical) pharmacists; however, this it has to be through communication with the attending clinical pharmacists.

Study design

The study was a retrospective review of the documented clinical pharmacists’ interventions in WWRC, which are defined as clinical pharmacist’s actions that directly resulted in alterations in patients’ care or therapy. All clinical interventions were directly sourced from the clinical intervention sheet, a component of each patient’s record in the Cerner electronic medical database. In cases where the clinical intervention sheet contained incomplete information, data was extracted from the patient’s file notes within the electronic medical records. The interventions were recorded by clinical pharmacists or clinical pharmacy specialists and subsequently validated by physicians. While staff pharmacists may propose interventions, these suggestions are documented through collaboration with the clinical pharmacists. The specific intervention categories defined in our system include: addition of another medication, discontinuation of a medication, switching to alternative medication, addition of a prophylactic agent during hospitalization, change in medication route, change in medication strength, change in medication dose, change in medication duration, change in medication frequency, addition of a lab test, addition of a serum level, and addition of a culture test.

Study population

This study assessed clinical pharmacist interventions provided to inpatients admitted to WWRC. The inpatient population was female adults, 18 years or older, who were admitted to the WWRC inpatient wards.

The study sample was observed over three distinct months: March 2018, July 15 to August 15, 2018, and January 2019. The rationale behind selecting these specific months was to align with HMC annual performance evaluation period, which typically occurs in February. This timing could potentially impact the documentation practices of clinical pharmacists.

Inclusion criteria

Women inpatients aged 18 years or older admitted to the WWRC during the specified data collection periods (March 2018, July 15 to August 15, 2018, and January 2019), including both obstetric and gynecologic patients.

Patients had at least one medication indicated for continued use during hospitalization, including first-time treatments.

All interventions received physician approval to ensure alignment with clinical guidelines and patient safety.

Exclusion criteria

Any interventions directly performed by a non-clinical pharmacist to maintain the integrity of clinical pharmacy practice.

Interventions that were not approved by a physician, regardless of supporting evidence, to ensure that all recommendations align with clinical standards.

Economic evaluationCost savings

Cost saving was defined as the reduced cost of therapy resource use because of clinical pharmacists’ interventions and was calculated based on a 3-month follow-up sampling duration. This was estimated by subtracting the total cost of therapy resource use “after” intervention from the total cost of therapy resource use “before” the interventions. Here, depending on what an intervention constitutes, the cost of a resource use can increase or decrease with the intervention. Further details on cost-saving calculations are demonstrated in Supplementary Table 1.

Cost avoidance

Cost avoidance was defined as the cost avoided because of preventing the occurrence of ADEs because of clinical pharmacy interventions, and it was calculated based on the 3-month study duration, by multiplying the cost of an ADE by the probability of the ADE happening. The cost of an ADE was estimated based on the assumption that it results in a 2-day additional hospital stay per patient, consistent with literature [12]. The estimation of the likelihood of ADE occurrence in the absence of intervention was calculated based on the Nesbit et al. method [18], and it used the following probabilities: 0 (none), 0.01 (very low), 0.1 (low), 0.4 (medium), or 0.6 (high). Further details on cost avoidance calculations and the Nesbit method are in Tables S1 and S2, respectively.

Total benefit analysis

Total benefit analysis was calculated as the sum of the total cost saving and total cost avoidance associated with all clinical interventions over a 3-month study follow-up period. The annual projected value of benefit was also calculated.

Expert panel members

The probabilities of ADEs to occur in the absence of clinical interventions was determined by an expert panel utilizing the method suggested by Nesbit et al. [18] (in Supplementary Table 2). The panel was composed of four clinical pharmacists and one physician in WWRC. All had more than 5 years of clinical experience in the field. The probability of an avoided ADE was estimated for each intervention by each panel member, and an average was calculated.

Perspective

The study was conducted from the perspective of the public WWRC hospital and, hence, only direct medical costs were used in the current analysis, excluding non-medical and indirect costs.

Cost inputs

The monetary values of medication-based and non-medication-based resources were obtained from the pharmacy department as well as the finance and costing department. Using the Qatari Health Consumer Price Index (Trading Economics), all costs were adjusted for the financial year 2024 and were presented in Qatari Riyal (QAR) and USD.

Sample size

Previous relevant literature research reports have not utilized a standardized sample size as this differs depending on variety of reasons including settings, context, and prevalence of the studied conditions. Economic evaluations, in contrast to clinical research, are concerned with making a cost estimate rather than testing hypotheses. Thus, even if underpowered, they still provide valuable information to guide decision-making [19]. It has been shown in relevant studies from the literature, especially those based on secondary/tertiary care hospitals [20], that the number of errors analyzed can range from less than 100 to less 500. On the basis of a preliminary investigation of the incidence of interventions in the study setting, we anticipated that a 3-month study period should provide sufficient time to collect more than 250 interventions.

Statistical analysis

Descriptive statistics were used to analyze baseline demographics. Depending on their normal distribution, numerical data were presented as mean ± standard deviation (SD) or median ± interquartile range (IQR). Categorical variables were presented as frequencies and percentages. In order to test for any significant difference among patients’ characteristics over the 3-month follow up, Kruskal–Wallis and Chi-Square tests were used. Statistical significance was determined based on p values of < 0.05 and 95% confidence interval (CI). All Statistical tests were carried out using the IBM Statistical Package for Social Sciences (IBM SPSS®26 software).

Sensitivity analysis

One-way sensitivity analysis was performed, with the targeted uncertain input of the cost of the ADEs, using an assigned ± 20% uncertainty range. Multivariate uncertainty analysis was performed by targeting the cost of the ADEs, using an assigned ± 20% uncertainty range, and probabilities of the avoided ADEs set by the expert panel, using an assigned ± 15% uncertainty range for any probability. Both sensitivity analyses were conducted via Monte Carlo simulation (1,000 iterations), using @Risk-5.7 (Palisade Corporation, NY).