The Scottish NHS has slashed diagnostic waiting times but must now ensure that services are as efficient as possible.

The number of people waiting more than nine weeks for key tests has fallen from 10,638 in July 2006 to two patients in July 2008, an Audit Scotland report published today shows.

Audit Scotland says NHS boards have achieved these reductions by using£50m of additional government funding and making longer-term improvements to how they provide services.

But the spending watchdog found that the efficiency of diagnostic services varied across boards and there was scope for NHS boards to make better use of resources. It also found that the NHS needs better information to compare the efficiency of services across boards.

Deputy auditor general for Scotland Caroline Gardner said: "The NHS has significantly cut diagnostic waiting times. The challenge now is to continue to improve diagnostic services as the NHS faces shorter waiting times targets.

"A lot of money is spent on diagnostic services and the NHS needs to ensure efficiency of these high-cost services."