Differences Between Palliative Performance Scale and Karnofsky Performance Scale Index
The Palliative Performance Scale (PPS) is a modification of the Karnofsky Performance Scale Index (KPSI) specifically designed for palliative care settings, with the key difference being that PPS includes additional domains like oral intake, level of consciousness, and self-care, while KPSI focuses primarily on functional ability and medical requirements.
Scale Structure and Scoring
The Karnofsky Performance Status (KPS) scale is an 11-level ordered scale (0-100) that assesses patients based on their health status, including activity, work, and self-care abilities. Lower KPS scores are associated with poorer survival and more serious illness 1.
The Palliative Performance Scale (PPS) was developed as a modification of the KPS specifically for palliative care settings, maintaining a similar scoring structure but with different descriptors more relevant to end-of-life care 2.
Key Differences in Assessment Domains
KPS primarily focuses on general functioning and medical care requirements as a measure of patient independence 3.
PPS expands beyond KPS by incorporating additional domains particularly relevant to palliative care, including:
Clinical Application and Setting
KPS was originally designed for and is widely used in oncology settings to quantify the functional status of cancer patients 3, 5.
PPS was specifically developed for use in hospice and palliative care settings where the traditional KPS had limitations, particularly regarding references to location of care and bed confinement 4.
The Thorne-KPS (TKPS), a modified version of KPS, was developed to address limitations when using KPS in home hospice settings by avoiding references to location of care and adding descriptors for assessing frequency of professional visits and proportion of time spent in bed 4.
Interchangeability and Correlation
There is a direct positive linear relationship between KPS and PPS, allowing them to be used interchangeably in many clinical contexts and within prognostic tools such as the Palliative Prognostic Score (PaP) and Palliative Prognostic Index (PPI) 2.
Studies have shown that PPS scores are often consistently lower than KPS scores and spread over a wider range of the scale when assessing the same patients, suggesting PPS may be more sensitive to functional changes in palliative care populations 4.
Prognostic Value
Both scales have demonstrated predictive validity for survival in cancer patients, with lower scores associated with shorter survival times 1, 5.
KPS is incorporated into the Palliative Prognostic Score (PaP) along with other factors such as dyspnea, anorexia, clinical prediction of survival, white blood cell count, and lymphocyte percentage to predict 30-day survival probability 1.
Some research suggests that the PPS may be a more objective and sensitive measure of functional performance specifically in home hospice patients 4.
Common Pitfalls and Considerations
Interrater reliability can be an issue with both scales, though training can significantly improve consistency. Studies have shown interrater reliability of 0.97 for KPS when used by trained observers 5.
The KPS has shown less ability than the Eastern Cooperative Oncology Group Performance Status (ECOG PS) to discriminate patients with different prognoses in some studies 6.
When converting between scales, discrepancies most commonly occur in the middle ranges of the scales, with stronger agreement at higher performance levels 4, 6.
The PPS may be more appropriate for palliative care settings as it avoids references to hospital care that can be problematic when assessing patients in home care settings 4.