Aim
The aim of this study is the cross cultural adaptation and psychometric validation of a Polish translation of PPSv2 tool (PPSv2-Polish).
Design
We obtained agreement and guidelines for the translation process from the Victoria Hospice Society, the owner of the tool.
The tool translation and back-translation were done in cooperation of three palliative care centers: St. Lazarus Hospice in Krakow, Medical University of Warsaw (Poland), and Jagiellonian University Medical College, Krakow, Poland.
The testing and retesting of PPSv2-Polish was performed by the hospice care team at St. Lazarus Hospice in Krakow (Poland).
Patient characteristics, including gender, age, primary diagnosis, and disease stage based on the Gold Standard Framework needs based coding (GSF; see Table 1) [5] assessed by the attending physician, were obtained from medical records. All participants were evaluated twice, on the first and third day, for test-retest reliability by the same member of the hospice care team at St. Lazarus Hospice in Krakow (Poland) (a trained and experienced palliative care nurse, psychologist, or physiotherapist), who cared for the patient. Additionally, on the first evaluation, two different care providers (each time by different types of professionals) independently evaluated the same patient to establish inter-rater reliability values. Each patient’s evaluation encompassed the PPSv2-Polish, which was compared simultaneously with 3 additional performance scales, considered the gold standard [6], to accomplish its external construct validity.
Participants
Among 223 patients consecutively admitted to an in-patient hospice (between September 1st and November 30th 2019), 200 (aged ≥18 years), who were Polish native speakers whose performance status was unlikely to change significantly during the nearest 3 days according to the attending physician, were recruited and enrolled in the study.
Measures
Palliative Performance Scale version 2 (PPSv2)
The PPS provides a functional assessment of a patient’s ambulation, activity level, evidence of disease, self-care, food/fluids intake, and level of consciousness. The PPS has 11 categories, from 100% (full mobile and healthy) to 0% (dead) in decrements of 10%. In 2006, PPS version 2 (PPSv2) was introduced after clarification of instructions for its use [7].
PPSv2-Polish translation process
A modified combined translation technique [8] of PPSv2 into Polish was applied, which consisted of 1) independent forward translations by a physician, a psychologist and a Polish native speaker, 2) team discussion on identified differences between these 3 versions until agreement, 3) independent backward translations by a physician, a psychologist and a native English speaker, and 4) second team discussion on any differences between the original and back-translated versions until all agreed that the two versions were semantically identical (Figure 1).
This method followed the Victoria Hospice translation guidelines sent to the authors. The discussed back-translated version was then preliminarily tested in the hospice on 20 patients to obtain the final version of the PPSv2 (PPSv2-Polish – see Additional file 1). The implementation process encompassed education of the medical staff participating in this study during one training session, based on the Victoria Hospice Society instructions sent to the authors, giving the opportunity to get feedback from the team members.
Karnofsky Performance Score (KPS)
The KPS ranking is an 11-point scale and runs from 100% - perfect health, to 0% - dead. While first published in 1948 [9] to evaluate the ability to survive chemotherapy for cancer, it has recently undergone several evaluation adjustments [10]. The KPS provides great consistency of ratings by different oncology professionals [11]. It may also serve as a life survival predictor [12]. Hovewer, it has not been validated in Poland yet.
Eastern Cooperative Oncology Group (ECOG) Performance Status (ECOG PS)
This scale, also called the World Health Organization (WHO) score, was published in its current form by ECOG in 1982 [13] to assess a patient’s level of functioning in terms of the ability to care for himself, daily activity, and physical ability, in order to measure the impact of the disease/treatment on performance status. It has a good intra and interobserver agreement in cancer patients' performance status assessment [14]. It consists of 6 categories, from 0 - fully active, to 5 - dead, and is simpler to use, may be clinically preferable in comparison to the KPS, [15] and is widely used in the literature, yet not validated in Poland.
Barthel Activities of Daily Living (ADL) Index
This "simple index of independence" was published in 1965 for measuring the improvement during rehabilitation of the chronically ill" [16]. The original version was modified in 1988 to a 20 point scale that measures in increments of 1 point: from 0 - fully dependent, to 20 - fully independent [17]. The final score can be multiplied by 5 to obtain a 100 point score, and it is proposed that scores of 0-20 indicate "total" dependency, 21-60 indicate “severe” dependency, 61-90 indicate “moderate” dependency, and 91-99 indicates “slight” dependency. It is already widely used as the measurement of daily living activities and has become a standard measure of physical disability in practice [18]. Ten categories are assessed: feeding, grooming, bathing, dressing, toilet use, presence of fecal incontinence, presence of urinary incontinence, transfers (e.g., moving from wheelchair to bed), walking on an even surface (or propelling a wheelchair if unable to walk), and ascending and descending stairs. This scale has been widely used, however, has not yet been adapted in Poland.
Statistical analysis
We summarized the baseline demographics using descriptive statistics and medians with interquartile ranges (IQR) in non-normally (according to Shapiro-Wilk test) distributed ordinal quantitative data. A Wilcoxon signed-rank test was used to compare test-retest of ordinal data in one sample in test-retest and inter-rater comparison. Non-parametric data within subgroups of patients were compared using a Mann-Whitney U test. The strength of the relationship between the test-retest variables, and between the tools scores and survival time were calculated with the Spearman’s rank correlation coefficient. The inter-rater reliability was estimated using Cohen’s kappa statistics. Data were analyzed using STATISTICA 13.0 (TIBCO Software Inc. 2017) data analysis software. A P-value of <0.05 was considered as the level for statistical significance. The sample size for this survey was based on general guidelines for conducting qualitative research [19] As there are no absolute rules for the sample size needed to validate a questionnaire a fair size of 200 patients was chosen.