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Validation of the Simplified Palliative Prognostic Index to Predict Survival for Advanced Cancer Patients in Home Hospice Setting

Background The simplified Palliative Prognostic Index (sPPI) substitutes a single item from the Communication Capacity Scale (CCS) for the delirium item of the original PPI. This study aimed to examine the validity of the sPPI for patients with advanced cancer in a home-based hospice care setting. Methods This study included 75 patients with advanced cancer who received home-based hospice care. We used medical records maintained by professional hospice nurses who had visited the patients in their homes. Based on their sPPI score, patients were divided into three groups—A (<4), B (≥4 and <6), and C (≥6)—to compare survival. Further, we investigated the sPPI’s accuracy using the area under the receiver operating characteristic curve (AUC) and sensitivity and specificity for 3- and 6-week survival. We used three sPPIs including different substitutions for the delirium item (two methods using the CCS and one using the Korean Nursing Delirium Screening Scale). Results The median survival was 60–61 days for group A, 27–30 days for group B, and 12–16 days for group C. The difference in survival was significant (P<0.05). The AUC was 0.814–0.867 for 3-week survival and 0.736–0.779 for 6-week survival. For 3- and 6-week survival, prognostic prediction showed sensitivities of 76.2%–90.9% and 76.3%–86.8%, and specificities of 64.2%–88.7% and 51.4%–70.3%, respectively. Conclusion The sPPI, which is measured by professional hospice nurses, has acceptable validity to predict survival for patients with advanced cancer in a home hospice setting in South Korea.


INTRODUCTION
In palliative care, the accurate prediction of life expectancy is important for patients, families, and healthcare providers. If life expectancy can be estimated more precisely, patients can plan the remaining years or months of their lives and prepare for their death. 1) Moreover, families can prepare to bid farewell to their loved ones and handle practical concerns such as the caregiving period and medical expenses. 2) In addition, it is important for healthcare providers to accurately predict life expectancy to determine treatment plans and provide appropriate medical care. 3) Accordingly, various tools for predicting the prognosis of patients with terminal cancer have been studied and developed. The Palliative Prognostic Index (PPI), 4) Cancer Prognostic Scale, 4) Palliative Performance Scale (PPS), 5) Palliative Prognostic (PaP) Score, 6) PaP Score with Delirium (D-PaP), 7) Japan Palliative Oncology Study-Prognostic Index, 8) and Prognosis in Palliative Care Study (PiPS) 9) model are some that have proven effective. Among them, the PPI is used worldwide for its simplicity and high predictive power. [10][11][12][13][14] The PPI was proposed by Morita et al. 15) of Japan and uses five variables: the PPS, oral intake, edema, dyspnea at rest, and delirium. The PPI does not include blood or imaging tests, and is thus applicable to patients in various conditions.
The diagnosis of delirium, which is one of the variables of the PPI, is based on the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV). According to the definition in the DSM-IV, patients are diagnosed with delirium if there is a change in consciousness and cognitive function, along with reduced attention and concentration. These symptoms appear within hours or days. 16) However, since the DSM is a diagnostic tool, it may not be suitable for quick assessment at the point of treatment, and it may be difficult for certain healthcare providers to make judgments based on the diagnosis. Morita et al. 17) demonstrated the utility of the Communication Capacity Scale (CCS) in measuring the ability to communicate in patients with delirium. Hamano et al. 18) demonstrated the effectiveness of the simplified PPI (sPPI), which replaces items related to delirium with the CCS. Comparing the sPPI and PPI, Hamano et al. 18) discovered that the sPPI's sensitivity and specificity of survival prediction within 3 weeks was 72.9% and 67.6%, respectively, while these values were 80.3% and 61.8%, respectively, at 6 weeks. In contrast, the PPI's sensitivity and specificity of survival prediction within 3 weeks was 66.2% and 76.6%, respectively, and within 6 weeks was 74.2% and 72.8%, respectively.
However, studies on the sPPI have been insufficient, and further research is needed to establish its validity in various environments.
Since the sPPI is easier to evaluate than the PPI, it may be more useful for patients in home-based hospice care, who are in an environment where access to diagnostic equipment or personnel may be limited. However, most previous studies have targeted inpatients receiving hospice care. While Hamano et al. 19) analyzed the utility of the PPI for patients in home-based hospice care, there are no such studies on the sPPI. Accordingly, the purpose of this study was to evaluate the validity of the sPPI's life expectancy prediction for patients in home-based hospice care at a university hospital in South Korea.

Subjects
The subjects of this study were 75 patients who received home-based hospice care from a university hospital from January 2019 to March 2020. The survival period was defined from the day when home-based hospice care began to the day of death. The patients were followed up for 6 months if they had survived at the end of the home-based hospice care period. This study was approved by the institutional review board of Chungnam National University Hospital (IRB approval no., 2018-08-023). Informed consents were collected from patients or their families.

Study Method
Three professional hospice nurses recorded the sPPI items upon their first home visit, and the additional assessment of delirium was made according to the Korean Nursing Delirium Screening Scale (Korean Nu-DESC). 20) The sPPI score was calculated using the PPS, oral intake, edema, dyspnea at rest, and CCS. The PPS was developed by modifying the Karnofsky Performance Scale and covers five aspects: ambulation, activity and evidence of disease, self-care, oral intake, and level of consciousness. 21) Based on the patient's overall condition, the score ranges from 0 (death) to 100 (normal); scores between 10 and 20 were given 4 points, scores between 30 and 50 were given 2.5 points, and scores ≥60 were given 0 points. In terms of oral intake, the patient received 2.5 points for severe reduction, 1 point for moderate reduction, and 0 points for normal intake. For edema, 1 point was given for presence and 0 for absence. For dyspnea at rest, 3.5 points were given for presence and 0 for absence. The CCS was divided into four levels: level 1, when explicit and complex communication was possible; level 2, when explicit but simple communication was possible; level 3, when there was a slight incoherency or meaningful communication was possible only with stimulation; and level 4, when speech was out of context or when there was no verbal response even with stimulation.
The presence of delirium was determined using the CCS; 4 points were given for presence and 0 point for absence. The total sPPI score ranged from 0 to 15.
The Nu-DESC is composed of five items: disorientation, inappropriate behavior, inappropriate communication, illusions/hallucinations, and psychomotor retardation. 22) A score between 0 and 2 was assigned according to the degree of each item, but a study that introduced the Nu-DESC in Korea showed that there was no clear standard for determining the severity of each item. 20) Hence, it was modified to have a maximum score of 5 points. In this study, the presence of delirium was identified by a score of ≥2 points on the Korean Nu-DESC based on previous findings. In addition, demographic data including age and gender, as well as medical history such as primary sites of cancer and treatment methods including surgery, chemotherapy, and radiotherapy, were investigated.

Statistical Analysis
Based on the study by Hamano et al., 18) the patients' sPPI scores were divided into three groups: <4 points, 4-6 points, and ≥6 points. The Kaplan-Meier survival curve was obtained and a log-rank test was performed to compare the prognosis. In addition, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated to verify the accuracy of the sPPI in 3-and 6-week survival predictions. The receiver operating characteristic (ROC) curve was constructed and the area under the ROC curve (AUC) was measured to verify the discriminative accuracy for 3-and 6-week survival.
There is currently no clear cutoff value for the classification of CCS levels to determine whether delirium is present. When a previous study defined levels 2, 3, and 4 (1/234) or levels 3 and 4 (12/34) as delirium, the accuracy was 87% and 75%, respectively. 18) In both cases, comparing the sPPI and PPI showed similar predictability; thus, using the 1/234 standard with simple clinical judgment was recommended.
However, according to the Korean Nu-DESC, the frequency of delirium detected was 16%, whereas the frequency after dividing the CCS levels into 1/234 and 12/34 was 48.0% and 4.0%, respectively. The frequencies of delirium obtained from the three methods-CCS 1/234, CCS 12/34, and the Korean Nu-DESC standard-were quite different. Therefore, the analysis was conducted by applying all three. The use of the following three sPPIs including different diagnostic methods of delirium detection, relatively easier methods than using the DSM-IV standard: (1) sPPI1: sPPI using the CCS 1/234 standard for delirium diagnosis; (2) sPPI2: sPPI using the CCS 12/34 standard for delirium diagnosis; (3) sPPI3: sPPI using a score ≥2 points on the Korean Nu-DESC for delirium diagnosis.
The analysis was performed using IBM SPSS ver. 24.0 (IBM Corp., Armonk, NY, USA), and the significance level for all statistical analyses was set at <0.05.

Characteristics of the Study Subjects
Of the 75 patients, 39 were male (52.0%) and the average age was 69.12 years. The most prevalent site of primary cancer was the lung ( Values are presented as mean±standard deviation or number (%).  empirically, a tool is deemed useful when the sum of the sensitivity and specificity is 150% or higher. 23) The AUC is used to confirm the overall validity of a tool, where the larger the area, the higher the valid-

Relationship between sPPI Score and Survival Time
ity. An AUC between 0.9 and 1.0 indicates that the tool is excellent; between 0.8 and 0.9, very good; between 0.7 and 0.8, good; between 0.6 and 0.7, sufficient; between 0.5 and 0.6, bad; and <0.5, not useful. 24) Therefore, the sPPI has utility for prognosis prediction. This study is the first of its kind to prove the utility of the sPPI in patients with termi- To date, there has been no study on the sPPI for patients receiving home-based hospice care. According to a study by Hamano et al., 19) which analyzed the utility of the PPI in patients receiving home-based hospice care, a life expectancy prediction of less than 3 weeks when the PPI score was ≥6 points and a life expectancy prediction of less than 6 weeks when the PPI score was ≥4 points showed a sensitivity of 60.0% and 70.6% and specificity of 87.0% and 71.9%, respectively. The sensitivity was lower as compared to values reported by Morita et al.,15) : 83% and 79% for 3-and 6-week survival predictions, respectively.
Among the 3-and 6-week survival predictions in this study, the best were those obtained from sPPI2, that is, including CCS levels 3 and 4 for the diagnosis of delirium. It showed a sensitivity of 77.3% and 76.3% and specificity of 88.7% and 70.3%, respectively; these values were higher as compared to previous studies, except for the specificity of the 6-week survival prediction. Furthermore, a multicenter study by Baba et al. 14) that analyzed the accuracy of the PaP, D-PaP, PPI, and PiPS showed an accuracy of 69.3%-79.5% across short-term survival (≤13 days or ≤21 days) and long-term survival (≥30 days, ≥42 days, or ≥56 days) in patients in home-based hospice care. In this study, the accuracy of survival predictions of 3 weeks or less and 6 weeks or less was 72.0%-85.4% and 69.3%-73.4%, respectively. Thus, the sPPI is considered to be as accurate as other tools. In particular, when the sPPI score was ≥6, the accuracy of the 3-week survival prediction was quite high. A future study that directly compares the sensitivity and specificity of the sPPI and other tools would clearly confirm the effec- When the PPI was first developed in 1999, it used the DSM-IV criteria, but the DSM-5, which was released in 2013, 29) entailed certain changes in diagnostic criteria for delirium. While the DSM-IV mentioned the disturbance of consciousness, the DSM-5 removed items related to consciousness level, instead focusing on the disturbance in attention and awareness. In a study that diagnosed patients with delirium using each DSM criterion and compared the mortality rate and length of stay, patients diagnosed with delirium using the DSM-5 and the DSM-IV accounted for 20.5% and 22.5% of the subjects, respectively. The mortality rate was highest when diagnosed using the DSM-5, while the length of stay was longest when diagnosed using the DSM-IV. 30 Despite such limitations, this study provides grounds for applying the sPPI, a single prognostic index, to patients with terminal cancer by expanding it to South Korean patients. Moreover, this study confirms that the sPPI has reasonable predictive power and is easy to use for hospice nurse specialists, who may not necessarily be doctors, to measure prognoses, thereby expanding the possibility of its clinical use and providing more appropriate palliative care.