Retrospective Cohort Study
Copyright ©The Author(s) 2018. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Oncol. Nov 10, 2018; 9(7): 140-147
Published online Nov 10, 2018. doi: 10.5306/wjco.v9.i7.140
Interconversion of two commonly used performance tools: An analysis of 5844 paired assessments in 1501 lung cancer patients
Kuruswamy Thurai Prasad, Harpreet Kaur, Valliappan Muthu, Ashutosh Nath Aggarwal, Digambar Behera, Navneet Singh
Kuruswamy Thurai Prasad, Harpreet Kaur, Valliappan Muthu, Ashutosh Nath Aggarwal, Digambar Behera, Navneet Singh, Department of Pulmonary Medicine, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh 160012, India
Author contributions: Prasad KT was involved in data collection and analysis, and initial drafting and final approval of the manuscript; Kaur H, Muthu V, Aggarwal AN, and Behera D were involved in data collection and gave final approval of the manuscript; Singh N was involved in conception of the study, data collection and analysis, initial drafting and final approval of the manuscript, and is the guarantor of the overall content.
Institutional review board statement: The manuscript was approved by Postgraduate Institute of Medical Education and Research, Chandigarh.
Informed consent statement: Informed consent was obtained from all the subjects.
Conflict-of-interest statement: All authors declare no conflicts of interest related to this article.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Navneet Singh, MD, Additional Professor, Department of Pulmonary Medicine, Postgraduate Institute of Medical Education and Research (PGIMER), Room No 4, Level IV, F block, Nehru Hospital, Chandigarh 160012, India. navneetchd@hotmail.com
Telephone: +91-172-2756826
Received: April 30, 2018
Peer-review started: April 30, 2018
First decision: June 6, 2018
Revised: August 6, 2018
Accepted: October 8, 2018
Article in press: October 8, 2018
Published online: November 10, 2018
Processing time: 194 Days and 16.4 Hours
ARTICLE HIGHLIGHTS
Research background

Performance status (PS) is an estimate of a subject’s ability to perform activities of daily living. Several tools are available to estimate the PS. Among them, the Karnofsky performance status (KPS) scale and the Eastern Cooperative Oncology Group (ECOG) scale are the most commonly used PS scales worldwide for patients with cancer. The KPS scale is an 11-point numerical scale, with scores ranging from 100 (normal functional status) to 0 (death), in decremental steps of 10. The ECOG PS scale is a 6-point numerical scale, with scores ranging from 0 (normal functional status) to 5 (death), in incremental steps of 1. Since the number of scoring points in each scale is different, these scales are not readily interconvertible.

Research motivation

PS is an important clinical factor which affects prognosis and influences treatment decisions in subjects with lung cancer. Hence, researchers who attempt to compare clinical characteristics or outcomes across different patient populations should ensure that their PS levels are matched. Failure to do so may result in erroneous conclusions. Most clinical studies employ only one of these two scales (either KPS or ECOG PS) in their study population for assessment of PS. When the PS scale used in the studies are different (either KPS or ECOG PS) this may lead to difficulty. Several investigators have tried to overcome this hindrance by suggesting KPS categories for interconversion to the ECOG PS scale. However, the performance of these suggested KPS categories has been variable.

Research objectives

We attempted to establish the KPS categories which would facilitate the interconversion of the KPS scale to the ECOG PS scale.

Research methods

We retrospectively analyzed the data of 1501 patients from a lung cancer clinic. In these patients, at every visit, paired assessments of PS had been made using both the KPS and ECOG PS scales by physicians. We also studied the performance of other KPS categories suggested in the literature, on our patient cohort. We used statistical methods called hit rate and weighted kappa to test the agreement between the KPS categories and the actual observations.

Research results

We found that the KPS categories 10-40, 50-60, 70, 80-90, and 100 were equivalent to ECOG PS categories of 4, 3, 2, 1, and 0 respectively. We also found that the agreement between the KPS categories suggested in the past literature (for interconversion to ECOG PS) and the paired KPS-ECOG PS assessments made in our cohort was variable.

Research conclusions

The current study is the largest set of paired KPS-ECOG assessments published in the literature in patients with lung cancer to date. The suggested KPS categories will facilitate interconversion of the KPS to the ECOG PS scale and will enhance communication between researchers utilizing either of the two scales.

Research perspectives

The KPS categories suggested in our study may be prospectively evaluated to test their validity. The applicability of the suggested categories may be evaluated in other populations to study the effect of cultural and regional variations.