To the Editor—Appropriate antibiotic use in surgical department is associated with reduction in morbidity and mortality.Reference Sartelli, Kluger and Ansaloni ¹ Challenges exist in conducting behavior-based studies of antibiotic stewardship, given the multifactorial decision-making associated with prescribing practices. Two theory-based behavioral constructs associated with sustained behavioral change are the Transtheoretical Model of Health Behavior Change (TTM) and the Theory of Planned Behavior (TPB).Reference Prochaska and Velicer ^{2 ,} Reference Ajzen ³ These behavioral theories were recently employed in successful implementation of a hand hygiene infection prevention campaign.Reference Apisarnthanarak, Eiamsitrakoon and Mundy ⁴ To potentially extend the application of these theories to medication prescribing practices, we performed an exploratory study to evaluate surgical care providers, categorized by TTM and by TPB, for association with appropriate antibiotic prescribing practice.

A prospective study was conducted at Thammasat University Hospital from January 1 to January 31, 2019. Surgical care prescribers of antibiotics were enrolled; de-identified data collection included demographics, indications, the rationale for antibiotic prescriptions, and prescribed drug modifications based on Tamma et al.Reference Tamma, Miller and Cosgrove ⁵ Appropriateness of antibiotic prescriptions was defined based on the criteria of Kunin et al.Reference Kunin, Tupasi and Craig ⁶ The source data for assessment was the hospital’s drug use evaluation (DUE) form. After DUE review, an in-depth interview using a standardized data collection tool was conducted with each prescriber by either a clinical pharmacist or infectious disease physician to explore antibiotic prescribing behavior based on the TTM and TPB. The interview with each prescriber focused on 1 antibiotic for treatment or 1 antibiotic for surgical prophylaxis. In TTM and TPB assessment, questions were modeled, and each domain was assessed based on previous publications (Supplement 1 online).Reference Prochaska and Velicer ^{2 –} Reference Apisarnthanarak, Eiamsitrakoon and Mundy ^{4 ,} Reference Charani, Edwards and Sevdalis ⁷

All analyses were performed using SPSS, version 19 software. The χ² or Fisher exact test was used to compare categorical variables. Independent t tests were used for continuous data. All P values were 2-tailed; P <.05 was considered statistically significant. To determine factors associated with appropriate antibiotic prescriptions, variables that had a significance level of P < .20 in univariate analysis were entered into multivariate logistic regression models. Adjusted odd ratios (aORs) and 95% confidence intervals (CIs) were calculated. Correlation between TTM and TPB behavior score were measured using Pearson correlation.

There were 92 antibiotic prescriptions assessed from 64 prescribers. Most antibiotic prescriptions (62 of 92, 67%) were for treatment of infection (Table 1); 70 prescribed antibiotics (76%) were deemed appropriate. The 3 most common reasons for inappropriate antibiotic prescriptions were (1) antibiotics choice for either treatment or surgical prophylaxis (n = 11, 50%), (2) treatment duration (n = 8, 36%), and (3) prescribed combination antibiotics (eg, a third-generation cephalosporins and metronidazole) for surgical prophylaxis (n = 3, 14%). Prolonged antibiotic use for surgical prophylaxis (>48 hours) (8 of 22, 36.3%) was common, particularly in neurosurgical procedures. Physicians who deescalated antibiotics had higher rate of appropriate antibiotic prescriptions, with an overall trend for inappropriate antibiotic prescriptions among physicians with higher levels of training. Notably, a higher proportion of inappropriate antibiotic prescriptions were identified among physicians who had no stated rationale for antibiotic selection.

For the behavioral assessments of prescribing practice, higher stages of TTM strongly correlated with appropriate antibiotic use. In contrast, there was no correlation between the total TPB score and appropriate antibiotic prescriptions (Supplement 1 online). Characteristics, antibiotic prescribing patterns, rationale for prescribing empirical antibiotics and modifying antibiotics, and behavior of prescribers are summarized in Table 1.

Table 1. Baseline Characteristics Among 92 Prescriptions in Perioperative Care Who Were Prescribed Antibiotics for Treatment or Prophylaxis

Note. N/A, not applicable; BLBIs, β-lactam-β-lactamase inhibitors; TPB, theory of planned behavior; TTM, transtheoretical model of health behavior

^a Other: surgical site infection, CNS infection, sepsis, osteomyelitis, prosthetic/ implant infection, ventilator associated pneumonia, ventilator associated tracheobronchitis, Clostridium difficile associated diarrhea, febrile neutropenia.

^b Combination antibiotics: carbapenem plus vancomycin, third generation cephalosporins plus metronidazole, third generation cephalosporins plus azithromycin, third generation cephalosporins plus clindamycin.

^c Other; dicloxacillin, penicillin G, TMP/SMX, fluconazole, ciprofloxacin.

^d Rationale including antibiotic prescribing for empirical and modification according to Tamma et al.Reference Kunin, Tupasi and Craig ⁶

By multivariate analysis, TTM prescribers in Action plus Maintenance (aOR, 7.95; 95% CI, 2.08–30.30) and prescribers considering patients as first priority (aOR, 4.02; 95% CI, 1.05–15.32) were associated with appropriate antibiotic prescriptions. Neurosurgical procedures (aOR, 0.13; 95% CI, 0.02–0.89) and antibiotic prescriptions for surgical prophylaxis (aOR, 0.15; 95% CI, 0.004–0.53) were associated with inappropriate antibiotic prescriptions. Prescribers staged in TTM Action plus Maintenance were also associated with appropriate antibiotic prescriptions for treatment and for surgical prophylaxis.

The major finding of this study is the identification of the strong correlation between the TTM stages of surgical care prescribers and appropriate antibiotic prescriptions. To our knowledge, this is the first study to evaluate TTM stages with medication selection. Based on the TTM framework, early-stage prescribers (precontemplation, contemplation, and preparation) have the potential opportunity to adopt appropriate antibiotic prescribing behaviors.Reference Charani, Edwards and Sevdalis ⁷ In contrast, the summary TPB scores did not correlate with antibiotic prescribing behavior. This finding contrasts with a systematic review of TPB domain scores reporting an association with antibiotic prescription behaviors.Reference Warreman, Lambregts and Wouters ⁸ It is plausible that the weight of the individual TPB determinants requires future refinement.Reference Warreman, Lambregts and Wouters ⁸ A second study finding was the key predictor of “considering patients as first priority” as a key predictor of appropriate antibiotic use. This finding suggests a patient safety and quality-improvement opportunity, while additional efforts may exist to minimize unnecessary antibiotic combinations for surgical prophylaxis and to shorten postoperative antibiotic duration.

The limitations of this study include acknowledgment of reported findings which may not be generalizable to other study populations, given the exploratory study design, small sample size, and single institutional study site. Additionally, despite structured interviews, inherent bias may have occurred in the TTM and TPB assessments, and have influenced the unweighted, cumulative TPB scores. Future work is planned for assessment of TTM stage–based prescriber interventions associated with antibiotic prescribing practices along with further characterization of the TPB intrapersonal behavior theory.