Hospitals must get better at explaining treatment, according to the Care Quality Commission, after a national survey of outpatients found many were left confused about tests, medicines and side effects.

The survey of outpatients treated at 163 acute trusts in England found improvements in key aspects of care including cleanliness, respect, dignity and involvement in decisions about care, with more patients describing care as “excellent” since the last similar survey in 2009.

However, the research by the CQC – based on the views of more than 72,000 patients who attended outpatient departments in April or May last year – also revealed a significant drop in performance in some areas, including when it came to ensuring patients felt fully informed about treatment.

More than a third of patients said they were unsure about the results of tests with just 62 per cent reporting staff had explained results in a way they could “definitely” understand.

Meanwhile, 22 per cent said they understood the explanation “to some extent” but 11 per cent said they did not understand their results at all and 5 per cent were never told.

There was a drop in the proportion who felt staff “definitely” explained what would happen during their treatment from 80 per cent in 2009 to 77 per cent in 2011, while the proportion who felt staff had “definitely” explained the risks and benefits before treatment fell from 72 per cent to 69 per cent.

In addition, 36 per cent said they had not been told about possible side effects from medication, down from 35 per cent in 2009. Just 43 per cent said they were completely sure about what side effects to look out for.

Other poor results were recorded when it came to scheduling appointments. More patients – 23 per cent – reported their appointment was changed to a later date by the hospital, up from 21 per cent in 2009.

And just a third – 33 per cent – of first-time outpatients were given a choice about appointment time and date.

CQC chief executive Cynthia Bower said the regulator was pleased to see improvements in basics like cleanliness and patient dignity.

“However, more still needs to be done to ensure that outpatients know what to expect, have tests and treatments explained to them clearly and are properly informed about the potential side effects of any medicines they are prescribed,” she added.

The survey results have been fed into over-arching scores for people’s experience of outpatients in 2011.

There were improvements in scores for safe and high quality care, relationships with staff, and cleanliness and comfort but a drop in the overall score for information and choice from 79.1 out of 100 the previous year to 78.6.