To the Editor: With the growing recognition of the positive effect of social support on the health outcomes of older people with chronic illness, healthcare interventions increasingly have incorporated a social support–enhancing component to promote care provided to older people.1 To conduct a sensitive evaluation of the effects of these support-enhancing interventions, an accurate measure of social support is needed, yet no reliable, valid Chinese social support measure has been published. The aim of this study was to establish the reliability and validity of the Chinese version of the Medical Outcomes Study Social Support Survey (MOS-SSS-C) in older patients with heart failure. The MOS-SSS is a 20-item questionnaire that measures the self-perceived adequacy of functional social support of patients with chronic illness.2 It covers the four dimensions of emotional-informational support, affectionate support, tangible support, and positive social interaction. It is scored on a 5-point Likert-type scale. The range in score is from 0 to 100, with a higher score indicating better perceived social support. The reliability and validity of the MOS-SSS have been widely reported.3 In this study, the criterion validity of the MOS-SSS-C was evaluated by measuring its correlation with the Chinese version of the Multidimensional Scale of Perceived Social Support (MSPSS-C). Construct validity was examined using factor analysis and correlation with the Chinese version of the Hospital Anxiety and Depression Scale (HADS-C). The internal consistency and 2-week test-retest reliability of the MOS-SSS-C were also determined. A convenience sample of 110 Chinese patients with a documented diagnosis of heart failure aged 60 and older with intact cognition (Abbreviated Mental Test score ≥6) was recruited upon discharge from the medical unit of a large general hospital as the main sample. The condition of heart failure was used because the study simultaneously validated another disease-specific measure for older Chinese patients with heart failure. This sample size was determined by requirements needed for factor analysis. The mean age±standard deviation of this sample was 77.9±7.8; 48.2% were male. Once eligible subjects were identified and consent to participate in the study had been obtained, the research nurse administered the MOS-SSS-C, MSPSS-C, and HADS-C before discharge. Retesting of the MOS-SSS-C took place 2 weeks later at the subjects' homes. All subjects completed the retest measurement. The demographic and clinical characteristics of the sample are summarized in Table 1. The MOS-SSS-C demonstrated significant correlation with the MSPSS-C (Pearson correlation coefficient (r)=0.82, P<.001) and the HADS-C (Pearson r=−0.58, P<.001). Confirmatory factor analysis supported the original four-factor structure of the MOS-SSS and further established construct validity. The Cronbach alpha for the overall MOS-SSS-C was 0.98; those for the subscales ranged from 0.93 to 0.96. The intraclass correlation coefficient for the 2-week test-retest reliability was 0.84. The MOS-SSS-C is easy to administer to older Chinese patients with chronic illness and generally requires 10 to 15 minutes for completion. It is evident that these results support the psychometric properties of the MOS-SSS-C in providing a multidimensional measure for the functional aspect of perceived social support in older Chinese patients with chronic illness. The instrument has high internal consistency and good stability. It is also a valid measure when compared with the MSPSS-C and with other constructs associated with social support such as the Chinese version of the HADS. Confirmatory factor analysis has supported the purported four-factor structure and further established the validity of the MOS-SSS-C. Nevertheless, it is important to recognize that, in this study, the psychometric properties of the MOS-SSS-C were established from a convenient sample of older patients with heart failure with intact cognitive ability recruited from the medical unit of a general hospital. Limitations therefore exist in generalizing the results of this study to other chronically ill people who are younger or community dwelling or in other rehabilitation settings. To conclude, social support has been recognized as a salient construct in healthcare research. Its various functions have an effect on the health outcomes of patients with chronic illness. This study provides evidence of the reliability and validity of the MOS-SSS-C when used in the older Chinese population with heart failure. It is recommended as a useful tool in the evaluation of social support in older Chinese patients. To further confirm its psychometric qualities, future studies should focus on examining the applicability of the MOS-SSS-C in other disease groups and in other settings. This research was funded by the Health Service Research Committee of Hong Kong (HSRC#S112002).