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Variability over time of haemostatic and other cardiovascular risk factors in patients suffering from angina
S D Pyke1, S G Thompson, R Buchwalsky
1Medical Statistics Unit, London School of Hygiene and Tropical Medicine, United Kingdom.
The variability of haemostatic factor measurements in patients presenting with angina pectoris is investigated. In all, 219 middle aged patients (almost all men) provided repeat measurements 2.5 years apart on a battery of haemostatic and haematological tests and other cardiovascular risk factors. Correlations between repeat measurements were lower than might be expected in a healthy population, reflecting a relatively large degree of variability within individuals over time. The highest correlations observed for haemostatic factors were for von Willebrand factor related antigen (r = 0.48) and fibrinogen (r = 0.45). The correlations were generally lower amongst patients who had undergone coronary surgery or angioplasty between the two measurements. We conclude that the underlying relationship of fibrinogen to coronary risk must be much greater than is generally appreciated, since even single measurements are found to be important predictors of risk, despite only moderate stability over time. The very low correlations for beta-thromboglobulin (r = 0.10) and platelet factor 4 (r = 0.03) which were observed in this study casts doubt on their potential usefulness as predictors of long-term cardiovascular risk.
The variability of haemostatic factor measurements in patients presenting with angina pectoris is investigated. In all, 219 middle aged patients (almost all men) provided repeat measurements 2.5 years apart on a battery of haemostatic and haematological tests and other cardiovascular risk factors. Correlations between repeat measurements were lower than might be expected in a healthy population, reflecting a relatively large degree of variability within individuals over time. The highest correlations observed for haemostatic factors were for von Willebrand factor related antigen (r = 0.48) and fibrinogen (r = 0.45). The correlations were generally lower amongst patients who had undergone coronary surgery or angioplasty between the two measurements. We conclude that the underlying relationship of fibrinogen to coronary risk must be much greater than is generally appreciated, since even single measurements are found to be important predictors of risk, despite only moderate stability over time. The very low correlations for beta-thromboglobulin (r = 0.10) and platelet factor 4 (r = 0.03) which were observed in this study casts doubt on their potential usefulness as predictors of long-term cardiovascular risk.