1. Cost utility of alternative Carbapenemase
Producing Enterobacteriaceae (CPE) screening
strategies in a low prevalence setting
Rahul Batra,1 Jonathan A Otter,1,2 Jonathan D Edgeworth,1 Simon D Goldenberg1
Centre for Clinical Infection and Diagnostics Research, King’s College, London and Guy’s & St Thomas’ NHS Foundation Trust, London, UK
Health Protection Research Unit (HPRU) in HCAI and AMR at Imperial College London.
Background
Infection with Carpapenemase Producing Enterobacteriaceae (CPE) is difficult to treat and results in poor clinical outcomes and excess financial cost to healthcare organisations.
Outbreaks in the healthcare setting can be prolonged and difficult to control, resulting in significant use of resources.
A number of international guidelines recommend screening patients for gastrointestinal carriage of CPE at the point of hospital admission to guide measures aimed at preventing spread (e.g. source isolation, use of personal protective equipment and enhanced environmental decontamination).
The cost utility of these screening strategies has rarely been considered.
Results
In all cases actual length of stay was measured which identified the number of patients who did not stay long enough to receive all three screens (all eligible patients were screened on admission and at 2 and 4 days following admission if they remained an inpatient).
All parameters obtained from the previous 15 week extended prevalence study [need to include a citation here] were extrapolated to cover a 12 month period.
Non-selective and chromogenic selective agar were significantly less sensitive than PCR, detecting 17% and 67% of true cases respectively.
Screening all admissions using PCR detected all cases at a cost of £4,417,595 per year or £34,328 per case detected.
Selective screening using either overseas hospital admission or admission to a high risk area would have the capacity to detect only 33% and 17% of true cases respectively, thus are not effective strategies.
Using current PHE risk factors would detect between 17% (non-chromogenic agar) and 50% (PCR) of true cases, depending on laboratory method. The total cost per case detected in this scenario ranged from £199,724 to £568,488.
In our low prevalence population, presumptive isolation results in a significant number of unnecessary isolation days (up to 158,818 per year, depending on screening strategy). Isolating only those found to be positive is more efficient, however risks transmission of of CRE in true cases before they have been identified. This could be particularly problematic for culture-dependent methods and there could be a potential role for a rapid point of care PCR method in some clinical areas.
The method most effective selective screening strategy was to include patients who had been admitted to hospital (UK or overseas) in the last 12 months. Using PCR, this strategy would detect 83% of true cases at a total cost per case detected of £137,868. The same strategy using chromogenic agar would detect 50% of true cases, at a cost per case detected of £215,475.
Aim
A cost utility analysis of several screening strategies was undertaken in our low CPE prevalence hospital population using data obtained in a previous extended prevalence study.
Methods
4006 inpatients were screened for CPE carriage using rectal swabs and three alternative laboratory methods:
Non-selective agar
Chromogenic selective agar
Multiplex PCR (Check-Direct CPE for BDMax™)
Risk factors for colonisation (previous hospital admission in UK or overseas, or admission to high risk areas such as ICU, renal and haemato-oncology) and length of hospital stay were collected. Calculated sensitivity of alternative laboratory detection methods were used with this data to model the effect on total patients screened, total screens performed (assuming three screens per patient), proportion of true cases detected, number of patients needed to screen to detect one case, presumptive isolation data required, and overall financial costs.
Conclusion
Although more expensive, a strategy of screening and presumptively isolating patients with any hospital admission (UK and overseas) in the previous 12 months, rather than using the current Public Health England recommended risk countries and areas, is more effective.
When PCR is used this strategy detects 83% of cases compared with 50% with the PHE strategy. Furthermore, it is likely to be easier to implement in practice rather than using a more complicated list of countries and risk areas, which is dependent upon having good epidemiological data to determine international prevalence.
Acknowledgements This study was funded by a grant from the Guy’s and St Thomas’ Charity and was supported by the NIHR Collaboration for Leadership in Applied Health Research and Care South London. JAO would like to acknowledge support from the NIHR HPRU) in HCAI and AMR.