WHY STOP? A prospective observational vignette-based study to determine the cognitive-behavioural effects of rapid diagnostic PCR-based point-of-care test results on antibiotic cessation in ICU infections

Objectives: Point-of-care tests (POCTs) for infection offer accurate rapid diagnostics but do not consistently improve antibiotic stewardship (ASP) of suspected ventilator-associated pneumonia. We aimed to measure the effect of a negative PCR-POCT result on intensive care unit (ICU) clinicians' antibiotic decisions and the additional effects of patient trajectory and cognitive-behavioural factors (clinician intuition, dis/interest in POCT, risk averseness).

Design: Observational cohort simulation study.

Setting: ICU.

Participants: 70 ICU consultants/trainees working in UK-based teaching hospitals.

Methods: Clinicians saw four case vignettes describing patients who had completed a course of antibiotics for respiratory infection. Vignettes comprised clinical and biological data (ie, white cell count, C reactive protein), varied to create four trajectories: clinico-biological improvement (the 'improvement' case), clinico-biological worsening ('worsening'), clinical improvement/biological worsening ('discordant clin better'), clinical worsening/biological improvement ('discordant clin worse'). Based on this, clinicians made an initial antibiotics decision (stop/continue) and rated confidence (6-point Likert scale). A PCR-based POCT was then offered, which clinicians could accept or decline. All clinicians (including those who declined) were shown the result, which was negative. Clinicians updated their antibiotics decision and confidence.

Measures: Antibiotics decisions and confidence were compared pre-POCT versus post-POCT, per vignette.

Results: A negative POCT result increased the proportion of stop decisions (54% pre-POCT vs 70% post-POCT, χ²(1)=25.82, p<0.001, w=0.32) in all vignettes except improvement (already high), most notably in discordant clin worse (49% pre-POCT vs 74% post-POCT). In a linear regression, factors that significantly reduced clinicians' inclination to stop antibiotics were a worsening trajectory (b=-0.73 (-1.33, -0.14), p=0.015), initial confidence in continuing (b=0.66 (0.56, 0.76), p<0.001) and involuntary receipt of POCT results (clinicians who accepted the POCT were more inclined to stop than clinicians who declined it, b=1.30 (0.58, 2.02), p<0.001). Clinician risk averseness was not found to influence antibiotic decisions (b=-0.01 (-0.12, 0.10), p=0.872).

Conclusions: A negative PCR-POCT result can encourage antibiotic cessation in ICU, notably in cases of clinical worsening (where the inclination might otherwise be to continue). This effect may be reduced by high clinician confidence to continue and/or disinterest in POCT, perhaps due to low trust/perceived utility. Such cognitive-behavioural and trajectorial factors warrant greater consideration in future ASP study design.