Holyrood 2016: How much does health matter?

How well is the NHS in Scotland performing compared with the rest of the UK?

This is one of the most fundamental questions for the NHS, and one of the most difficult to answer.

The NHS is run very differently in England, Wales and Northern Ireland but it's also monitored differently and that makes it very hard to compare. For example, survival rates for cancer and heart attacks are not comparable, and many waiting time targets also vary.

Perhaps the best measure we have is how satisfied patients are. The British Social Attitudes Survey regularly asks people that question, and for several years, Scots have expressed higher satisfaction than their counterparts in England and Wales (the survey does not cover N. Ireland.)

It's also worth remembering that nine in 10 people who've actually had recent treatment say they're happy with it. (Source: Scottish government inpatient experience survey, 2014)

How does the NHS in Scotland compare with other countries?

Earlier this year the Organisation for Economic Co-Operation and Development published a report which looked at the performance of health systems in the UK.

It said that Scotland had many innovative policies, although it should have more independent scrutiny of standards. It pointed out that the quality of healthcare in Scotland is no better than average when it came to international benchmarks of quality.

The independent health think tank, the Nuffield Trust, has looked at the performance of Scotland's NHS ahead of the Holyrood elections.

Its Policy and Public Affairs Analyst, Mark Dayan, says that health spending across the UK is quite low for a developed country.

He explained: "The Scottish NHS runs at relatively cheap rates by international standards. At the same time population need is growing and that will create tension which continues to rise.

"So, in the longer term, there needs to be some thought... particularly with Scotland having more of its own fiscal powers now, about whether there's action the Scottish government should take to do something about that."

What are the key issues politicians need to tackle?

There's a consensus that the NHS is facing great challenges:

The population is ageing. Medicines are more effective but come with a much higher price tag. The same goes for technology. And we're expecting treatment to be safer, quicker, and more convenient than ever.

Spending on the NHS has increased (at varying levels) and it has never had more staff. Yet, because of increasing demand, some areas are still understaffed.

One example is radiology. Radiologists used to be the folk who made a diagnosis by looking at your x-ray or ultrasound.

Now the scope of their work has expanded hugely. Imaging has become much more precise, but also radiologists now use their understanding of scans to carry out life-saving treatment.

The number of radiologists has risen by nearly 2% since 2012, but demand has risen by 10% a year.

Dr Grant Baxter says they're under intense pressure: "We can treat cancers now, that used to be treated surgically, simply by putting a little needle into the patient and either heating it up to a high temperature or cooling it down to a low temperature and killing that tissue.

"So there's a lot of different things that we do, it's a lot more time consuming, and therefore, we need a lot more radiologists to do this work."

So politicians face some key questions, and tough choices. Are they going to cut costs, or spend more? How will they stop costs spiralling out of control? And what choices do you want them to make, to ensure the NHS has a healthy future?

So, what are the parties saying?

Leaders of the SNP, Scottish Labour, Scottish Conservatives, Scottish Lib Dems and the Scottish Greens have been saying why the health service would be safe in their hands.