An interesting modelling study has quantified the size of the CPE iceberg lurking under the water when CPE is only detected by clinical cultures and no active screening is done. And the CPE iceberg is larger than you may think!

There’s a huge range of approaches to CPE detection, ranging from relying on clinical cultures from infections to detect CPE (aka passive surveillance) through to an extensive screening programme (aka active surveillance/screening). Whilst it is recognised that clinical cultures and local screening performed around detected cases will leave some ‘silent carriers’ out there, it’s difficult to quantify what we can’t measure (i.e. the silent carriers). This is where modelling can come in to help us to quantify the unknown.

The study was performed in Orange County in California, using an established agent-based transmission model including all healthcare facilities in the County (23 acute care hospitals, 5 long-term acute care hospitals, and 74 nursing homes). The model evaluated what would happen with the trend of CPE carriers – detect and ‘silent’ – if no active screening was done and CPE was detected only through clinical cultures. The study found, unsurprisingly, that many CPE carriers were silent – but the interesting finding was that the number of silent carriers rose faster than the number of detected carriers (see the Figure). Five years into the model, for every carrier detected by clinical cultures, there were 5 silent carriers.

Figure: The scale of the CPE iceberg of silent carriers in all Orange County hospitals.

Of course, a model can only be as good as the accuracy of the parameters that are entered. But these findings reinforce the need for active screening to detect CPE carriers to prevent a CPE iceberg sinking your ship!