When modelling and planning to achieve referral-to-treatment waiting time targets, should we model the entire wait in one lump, or split out the outpatient, diagnostic and inpatient/daycase elements?

Modelling in one lump has its attractions. It matches the waiting time target, and it greatly reduces the amount of modelling we need to do. So under what circumstances could we do it?

Firstly, the same referral-to-treatment pathway would need to be followed by nearly all the patients. If some need a diagnostic and some don’t, or if some attend outpatients at a different hospital, or if some go round a follow-up loop before moving on to the next stage, then modelling in one lump won’t work at all well.

Secondly, we must be running a pure modelling exercise that is divorced from management decision-making. The results of modelling in one lump will tell us nothing about admitted patient capacity, or tariff costs, or the waiting times that must be achieved in outpatients. So modelling in one lump greatly reduces the usefulness of the results.

Thirdly, we would need to model correctly the different reasons why some referrals do not end up as admissions. Some miss their appointments, some are discharged at outpatients or after their diagnostic, some are removed while waiting for their admission. Each of these dropouts will have a different impact on scheduling and waiting times.

So if modelling in one lump is such a bad idea, how do we resolve the fact that our referral-to-treatment target is one number, but we have two or three stages to model along the pathway?

It is certainly a good idea to split the overall target up, and apply each component as the target for each stage along the pathway. For instance, if we have an 18-week target for an outpatient-diagnostic-inpatient pathway, we might allocate 6 weeks for each stage. Then we can plan the capacity and booking templates for each stage separately. (If we tried to leave the target undefined for each stage, and manage each individual patient ad hoc within the overall target instead, there is the danger that outpatient waits would drift upwards in an unplanned way, leaving diagnostics and inpatients with all the burden of achieving the target.)

Sometimes we may lack accurate data at the diagnostic stage, in which case we can allow a reasonable time for it (say, 6 weeks), and then divide the remaining 12 weeks between outpatients and inpatients. Gooroo Planner can work out the optimum split, but usually it is better to allow more time for the outpatient stage because reducing outpatient lists causes an immediate knock-on to the inpatient list.

All in all, it is usually better to model each step of the pathway separately.