Patient characteristics.

<p>Values are reported as number of subjects, proportions (percentage) or median (10–90%).</p><p>*VAS = visual analogue scale.</p>†<p>Weak opioids = codeine or tramadol, or a non-daily intake of strong opioids.</p>‡<p>Strong opioids = morphine, oxycodone, methadone, fentanyl, ketobemidone.</p><p>Patient characteristics.