Kong W H, Llewellyn-Thomas H, Naylor C D
University of Toronto Medical Faculty, Ontario.
Can J Cardiol. 1992 Nov;8(9):947-53.
To assess the internal logic (content validity) of the Canadian Cardiovascular Society (CCS) scale for grading angina pectoris.
Forty-one consenting patients with stable angina of at least two months duration, admitted to a tertiary centre for coronary angiography.
Patients completed a supervised questionnaire with closed-ended questions. Key questions included: usual numbers of blocks walked on the level or flights of stairs climbed before onset of chest pain; frequency with which chest pain occurred at the usual threshold distance; presence of rest pain; and influence of modifiers suggested for class II of the scale such as walking uphill and into the wind.
Agreement of four questionnaire-defined 'stair-climbing grades' and 'walking grades' was statistically significant (P < 0.001) but only 37% better than expected by chance alone (weighted kappa). Frequency of angina at a patient's self-defined exercise threshold varied; only 22 of 41 patients (54%) had symptoms always or often. Higher classes of angina were more likely to be associated with frequent symptoms at threshold, eg, class I/II, six of 23 versus class III/IV, 16 of 17; 2P = 0.00002). Pain at rest was reported as 'definitely' present by 23 of 41 patients, and was similar in incidence across angina classes. All suggested modifiers reduced distances walked in a significant majority of patients (P values uniformly < 0.01) except for walking in the first few hours after awakening. However, the proportions of subjects for whom these factors were relevant were statistically similar for all angina grades, rather than for class II patients alone.
These findings suggest that internal inconsistencies in the CCS scale are identifiable with simple validity checks. Further research appears warranted to improve this popular and useful clinical tool.
评估加拿大心血管学会（CCS）心绞痛分级量表的内在逻辑（内容效度）。
41名同意参与研究的患有至少持续两个月稳定型心绞痛的患者，入住一家三级中心进行冠状动脉造影。
患者完成一份带有封闭式问题的监督问卷调查。关键问题包括：胸痛发作前在平地上行走的街区数或爬楼梯的层数；在通常的阈值距离时胸痛出现的频率；静息痛的存在情况；以及量表II级所建议的修正因素（如上坡行走和迎风行走）的影响。
问卷定义的四个“爬楼梯分级”和“行走分级”之间的一致性具有统计学意义（P < 0.001），但仅比随机预期高37%（加权kappa值）。患者自行定义的运动阈值时心绞痛的频率各不相同；41名患者中只有22名（54%）总是或经常出现症状。较高等级的心绞痛更可能与阈值时的频繁症状相关，例如，I/II级，23名中有6名；III/IV级，17名中有16名；P = 0.00002）。41名患者中有23名报告“肯定”存在静息痛，且各心绞痛等级的发生率相似。除了醒来后最初几个小时行走外，所有建议的修正因素在绝大多数患者中都减少了行走距离（P值均< 0.01）。然而，这些因素相关的受试者比例在所有心绞痛等级中在统计学上相似，而不仅仅是II级患者。
这些发现表明，通过简单的效度检查可以识别CCS量表中的内在不一致性。似乎有必要进行进一步研究以改进这一常用且有用的临床工具。
