The literature and research base for palliative care is increasing rapidly.  This evidence has the potential to influence clinical practice. However, as with other clinical fields, it is important to consider whether there are any circumstances of the individual patient or group of patients that could affect how the evidence is applied. These issues are discussed in the literature in terms of external validity, generalisability or transferability of evidence. 
In palliative care, where the aim of care is not curative, patient wishes and the care context can be particularly important. For example, prescribing decisions may be informed by the site of care of the patient such as residing in an aged care facility or being cared for at home. Decision making therefore requires not only an understanding of the relevant evidence but an active understanding of the underlying disease status, confounding or co-morbid factors and the individual’s physical, emotional and social issues.
The difficulties that confront clinicians in determining how to apply research evidence to an individual patient also reflect the broader considerations in developing research evidence within the discipline. In palliative care where symptom management and quality of life are the main goals of patient care, establishing clinical outcomes that can be both measured and are meaningful for the patient and the clinician can be challenging. 
It is unclear whether there are universal patient characteristics among those receiving palliative care and if not, how these might influence generalisability. For example, are findings for those living with advanced cancer equally generalisable to those living with end-stage renal disease?
At present much of the evidence that supports palliative care practice has been studied with specific segments of the palliative care population. this includes cancer patients or frail aged, or symptom studies in non-palliative populations such as those with chronic non-malignant pain. However, there can be different underlying pathophysiologies. This is further confounded by disease trajectory, morbidity and short life expectancy. These factors can affect the mechanisms of the symptom, symptom expression and the effect of an intervention.
In short, just as appraising the quality of research evidence is an important part of evidence-based practice, so is understanding its applicability within the palliative care environment and the individual patient context.