As the Scottish Government tries to reverse the rampant growth in outpatient waiting times, it runs the risk of sinking both of its higher-profile targets.

Those targets are: the legally-binding Treatment Time Guarantee (TTG), which promises that inpatients and daycases will always be treated within 12 weeks of the decision to treat; and the referral to treatment (RTT) target that 90 per cent of treatments will be given to patients who have waited less than 18 weeks since referral.

Outpatient waits have been soaring in Scotland since March 2012, oddly without anyone in the media or the Scottish opposition appearing to notice. Last year that growth turned explosive, with the number of over-12-week waiters increasing five-fold in the nine months to December. Yes, five-fold. Nor are the numbers small: over-12-week waiters now stand at nearly 10 per cent of the total outpatient waiting list.

Still-waiters over 12 weeks. All figures in this analysis exclude Lothian Health Board, who had an extraordinary waiting times scandal in 2012 which would dominate much of the time series if included.

But this is just the tip of the iceberg. Its rise is propelled by larger forces happening below the surface: the total size of the outpatient waiting list is rising inexorably.

Total still-waiters

It is the growth in the total waiting list that needs to be stopped, by bringing recurring activity back into line with demand. Only then can a one-off waiting list initiative be effective, and shrink the list so that short waits are sustainable once again.

But there is a problem. As soon as Scotland un-dams the stream at the outpatient stage, it will release a torrent of pent-up demand onto the inpatient and daycase waiting lists. The Scottish NHS is already showing signs of difficulty at holding down inpatient and daycase waits, and releasing this backlog could tip the TTG into large-scale breach.

Also, if large numbers of long-waiting outpatients suddenly appear on treatment lists, that will cause the RTT target to fail by an even larger margin than at present; the TTG means that Health Boards will have no option but to treat them, even though they are long-waiters whereas the RTT target favours treating short-waiters. Treating them is the right thing to do, of course; but in the topsy-turvy world of RTT targets it is discouraged.

How big a problem?

We can have a go at quantifying the knock-on effects on the TTG using Gooroo Planner. I have modelled the activity needed to return the outpatient and inpatient waiting lists to the last point where they were nearly compliant with the 12 week targets, choosing the March 2011 list size for outpatients, and the September 2013 list size for inpatients/daycases. (As elsewhere in this analysis, all figures exclude NHS Lothian who have been a special case in recent years; also the data going into the model is not perfect so the results are intended only to illustrate the likely magnitude of the task in hand.)

To return to 12 week compliance in December 2015, I estimate that outpatient activity needs to rise by 7 per cent in 2015, compared with 2014 activity levels (that’s a 2 per cent recurring increase, and a further 5 per cent non-recurring activity to shrink the list).

Meanwhile, inpatient/daycase activity needs to rise by a whopping 11 per cent (that’s 4 per cent recurring, 5 per cent non-recurring to keep up with the outpatient surge, and a further 2 per cent non-recurring to shrink the list). If inpatient/daycase activity didn’t increase at all, then the extra outpatient activity would cause waiting times to crash through the TTG to over 20 weeks, with the number of TTG breaches reaching around 27,000.

As the old joke has it, you wouldn’t start from here. The pressures in outpatients, though so far ignored in the public debate, won’t be ignorable for much longer. Action will have to be taken to deal with outpatients, in spite of the knock-on pressures for the TTG and RTT waits. It would have been better to start tackling these growing backlogs back in 2012 when I first raised concerns about them, or in 2013 when the trend was well established, but we are where we are.

On top of that, this year we have the UK General Election, and next year is the Scottish Parliament Election. Waiting times in Scotland are all going to get rather interesting.

(All data from ISD Scotland)