Data Sources
Population Data BC provides deidentified administrative data capturing individual-level health and health-services related information on nearly all 5.4 million BC residents.28 Access to this data provided by the Data Stewards is subject to approval but can be requested for research projects through the Data Stewards or their designated service providers. This study used six datasets provided by Population Data BC. The Medical Services Plan (MSP) Consolidation File provided demographic information, such as age, location of residence, and administrative sex, for all individuals insured under BC’s publicly funded provincial health insurance plan29 The MSP (Payment Information) file provided data on all medically necessary services provided by physicians and nurse practitioners through the province's fee-for-service system, including corresponding International Classification of Diseases-9 (ICD-9) diagnostic codes and billing codes.30 The Discharge Abstracts Database (DAD) provided data on acute care discharges and day surgery cases and the corresponding ICD-10 diagnostic codes.31 PharmaNet provided data on all prescription drug dispensations from BC pharmacies and physicians32 The Vital Events and Statistics Births and Deaths datasets included all births and deaths registered in the province which were utilized to restrict the cohort to only those alive during the full study period.33,34 All inferences, opinions, and conclusions drawn in this publication are those of the authors, and do not reflect the opinions or policies of the Data Stewards.
Study Period
We focused on physician visits and drug dispensations from January 1, 2022, through December 31, 2022 when the influence of the COVID-19 pandemic and its associated distancing measures had largely diminished.35 By early 2022, parallel virtual and in-person care had become the norm for many physicians. Data from 2020 and 2021 was analyzed to capture baseline medication dispensation patterns, physician visits for UTIs, and comorbidities.
Study Population
Our study population included all BC residents diagnosed with a UTI during the study period. We restricted our analysis to visits conducted by family physicians and differentiated between individuals who received care virtually and those who received care in-person. Individuals covered through federally funded programs, such as First Nations Health Benefits, were excluded as our dataset did not include their prescription drug use.
We defined a UTI diagnosis as an outpatient encounter in the MSP file with a urinary infection-related ICD-9 diagnostic code. Encounters were categorized as virtual or in-person based on BC fee-item codes that indicate mode of service delivery. These diagnostic and fee-item codes can be found within the supplemental material [see supplemental material Tables S1 – S3]. These billing codes distinguish between virtual and in-person visits, but are unable to identify the specific virtual care modalities (e.g., telephone versus video call).
We linked prescription drug dispensations from PharmaNet to a physician visit for UTI if the medications were filled within two weeks following a family physician visit. A two-week window was selected because an estimated 82% of patients in BC fill their prescriptions within two weeks of a primary care encounter.36 Moreover, given the acuteness of UTI symptoms, there it is unlikely that patients would delay filling antibiotics prescriptions beyond this timeframe.37,38
Outcomes of Interest
We examined changes in the following outcomes per visit: 1) the likelihood of antibiotic dispensation; 2) the likelihood of broad-spectrum antibiotic dispensation; and 3) the number of days of nitrofurantoin treatment dispensed. As antibiotics are not always indicated for treatment of UTI-like symptoms and nitrofurantoin, a narrow-spectrum antibiotic, is recommended for its treatment when antibiotics are indicated, these outcomes allowed us to assess prescribing patterns at increasing levels of granularity. We defined broad- and narrow-spectrum antibiotics utilizing a list of all common antibiotics and their spectrum classification obtained from the British Columbia Centre for Disease Control (BCCDC). Figure 1 shows the analytic cohort size and flow of observations as the data were matched and subset by outcome.
Statistical Analysis
We used propensity score matching (PSM) to construct cohorts of patients that had virtual and in-person primary care visits for UTI. Propensity-score (PS) methods are powerful commonly used tools in observational studies to reduce bias and confounding when estimating treatment effects. The PS represents the probability of receiving the treatment of interest given a set of observed baseline characteristics. By matching individuals with similar PS values, treated and untreated observations can be assembled into comparable groups that are balanced on measured covariates.39 PS is particularly useful in our study as the availability of comprehensive administrative data allowed for accurately match our two groups and mitigate confounding by indication. We constructed three PSM models using “greedy” matching and evaluated covariate balance for each cohort corresponding to our three outcomes. A standardized mean difference of 0.1 was used as the threshold to indicate a negligible difference between the treatment and control groups, following standard guidelines.39 Our final PSM model for all cohorts used greedy
1:1 matching with a caliper of 0.25 of the logit of the propensity score, incorporating the following covariates: sex, year of birth, most responsible physician (whether the physician attending the UTI-related visit was the individual's most commonly seen physician), binary indicators for prior UTI visit and UTI-related dispensation in the two years prior to the visit of interest, BC health service delivery area (HSDA) (16 geographic subdivisions of BC health regions), neighborhood income decile as defined by the MSP Consolidation File, Charlson Comorbidity Index as a continuous measure, and the proportion of visits conducted virtually by the physician attending the UTI-related visit. For the type and days of antibiotic prescribed outcomes, the number of prescriptions dispensed in the two years prior to a dispensation for UTI in 2022 was also included.
Variables were selected based on their established association with virtual care including sex, year of birth, geographic location, and income.40–42 Additional variables (i.e., Charleson comorbidity index, proportion of visits conducted virtually by the attending physician) were included based on their likely influence on the outcomes, informed by clinical and empirical considerations.
We applied three Generalized Estimating Equation (GEE) regression models on the matched dataset: two GEE logistic models assessing the association between virtual care and (1) antibiotic dispensation and (2) broad vs. narrow spectrum antibiotic use for UTIs, and one GEE linear model examining the number of nitrofurantoin days dispensed. All GEE models assumed an exchangeable correlation structure with observations clustered by patient and practitioner. Outcomes included a binary indicator for any antibiotic dispensation, a binary indicator for antibiotic spectrum (broad vs. narrow), and a numeric variable for duration of nitrofurantoin. Each model included the same covariates used in the PSM to ensure consistency and account for any residual confounding.
The analyses in this study were performed using SAS Version 9.4. This study was approved by The University of British Columbia Behavioural Research Ethics Board (certificate number: H24-00177).
Sensitivity Analyses
The sensitivity analyses used the full unmatched dataset, as well as inverse probability of treatment weighting (IPTW) followed by the same analysis.43 IPTW is an alternative PS method in which the inverse of the PS is used as statistical weights to create a sample that upweights samples with lower probability of occurring as predicted by the covariates, and vice versa. This helps balance confounding across exposure groups, enabling an unbiased estimate of the treatment-outcome relationship.39 These methods allowed us to assess the robustness of our results to the unmatched data as well as different PS-based approaches.