PTLs have been around since the early 2000s as a tried-and-trusted way of achieving waiting time targets.

What are they? The name doesn’t tell you much (depending on who you ask, PTL stands for Patient/Primary Targeted/Targeting/Tracking/Treatment List) but the concept is easy enough to explain:

Pretend it’s the 1st of February. In 4 weeks time, on the 1st of March, you want to have no patients waiting longer than 18 weeks since referral. All the patients who could possibly breach that target have already waited over 14 weeks. You know who they are, and the “PTL” is the list of their names. If you book everybody on the PTL in for treatment during February, then (so long as you don’t cancel any) you are guaranteed to achieve the target. Simple.

But this deceptively simple approach creates problems of its own.

Firstly, if you have a serious waiting time problem, then it is very difficult to find slots for all those patients. You might end up using slots that should really be kept aside for urgent patients who haven’t arrived yet. If urgent patients end up being delayed as a result, then you have created a clinical risk that could result in patients being harmed. This is a serious matter which a good booking system should be designed to avoid.

Secondly, when booking the PTL, your main concern is to find slots in February. Exactly which patient goes into which slot may be considered less important. But if you book routine patients out of order then the maximum waiting time goes up: those lucky patients who squeeze in for treatment at 14 and 15 weeks are jumping the queue on those waiting longer, and we know that queue-jumping pushes up maximum waiting times. So at next week’s meeting you will have more difficulty clearing your PTL, even though your underlying waiting time pressures have not changed.

PTLs manage long-waits in batches and at the margins

These problems arise because you are managing your long-wait problem in batches and at the margins, and your actions have unintended consequences for the rest of the system. It would be better to manage the whole system continuously in the right way, and so achieve the best possible waiting times safely and consistently.

If this holistic approach means that you can achieve 12 weeks, then you will. (You might not have realised it was possible using PTLs.) If the best you can achieve is 20 weeks, then you have a problem; but your planning and monitoring systems should have picked up this pressure already and pointed to solutions for relieving it (perhaps by moving resources from those services that can achieve 12 weeks).

What if your waiting list is just too huge to achieve 18 weeks safely and continuously? Then your problem is not so much waiting list management, but a mismatch between supply and demand that needs to be tackled together with commissioners.

While you’re dealing with that, you need to ask yourself how you want to fail in the meantime. You are faced with three main choices:

1. carry on treating routine patients in turn even if they all wait over 18 weeks;
2. drip-feed your long-waits through the system so that at least you’re achieving the headline target (90% of admissions within 18 weeks) while the backlog gets worse; or
3. squeeze so hard that urgent patients end up being delayed.

The first is the high moral ground, and the holistic approach; the second is understandable; the third is surely indefensible. PTLs, unfortunately, are most likely to lead you towards the third.

This post first appeared at HSJ blogs