Patients' experience of NHS care is more patchy and variable than suggested by national surveys, research by the King's Fund has found.
A new report by the think tank says most patients have a mixed experience while they are using services.
It says information and evidence is limited and more data is needed to understand the variations.
Seeing the Person in the Patient is based on interviews with staff and patients, as well as a review of surveys and literature.
None of the interviewees' experiences were "wholly good or wholly bad", it says.
"The defining feature of patients' experience of care in all kinds of settings was that it was unpredictable and unreliable. Almost everything depended on who was on duty, and beyond that, who was in charge: both factors that to the patients seemed unpredictable."
A large majority of respondents to national patient surveys describe their overall care as good, very good or excellent.
The King's Fund published the report today to launch its Point of Care programme, which calls for increased efforts to study and improve experience.
There needs to be a shift in culture at all levels, it says, and staff are urged to "see the person in the patient".
NHS management factors
The report says several factors in management are important. "The actions and words of senior hospital leaders… have a profound influence on what happens to patients.
"They shape the culture of the hospital: the priorities of managers and staff; how they behave, towards each other and towards patients and families; and how staff feel about the services they provide and the organisation."
Managers should set direction, create an open and team-working culture, maintain governance and have adequate information at team and specialist level.
"Working with patients, their families, staff and the leadership within hospitals we hope that the Point of Care programme will help to transform what it is like to be cared for in hospital."
Programme director Jocelyn Cornwell, who wrote the report with researcher Joanna Goodrich, said: "Staff come to work intending to provide the quality of care they would want for themselves and their families. But today's hospitals are vast, time is at a premium and in these busy 'medical factories' care of the person can unfortunately get squeezed out."