Title: Lipid Re-screening: What Is the Best Measure and Interval?
Topic: Prevention/Vascular
Date Posted: 4/22/2010
Author(s): Takahashi O, Glasziou PP, Perera R, et al.
Citation: Heart 2010;96:448-452.
Clinical Trial: No
Study Question: What is the long-term true change variation (‘signal’) and short-term within-person variation (‘noise’) of the different lipid measures and the optimal interval for lipid re-screening?
Methods: A retrospective cohort study was conducted from 2005 to 2008 at a medical health check-up program in Tokyo. A total of 15,810 apparently healthy Japanese adults not taking cholesterol-lowering drugs at baseline underwent an annual measurement of fasting serum lipids. Measurement of the ratio of long-term true change variation (‘signal’) to the short-term within-person variation (‘noise’) was determined for individual lipid components and the ratio of total cholesterol (TC) to high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) to HDL-C.
Results: At baseline, 53% were male; mean age was 49 years; body mass index (BMI) was 22.5 kg/m2 [standard deviation (SD) (3.2)]; mean TC level 5.3 mmol/L (0.9 mmol/L), triglycerides 1.1 (0.8); and mean ratio TC/HDL and LDL/HDL level at baseline were 3.5 (1.0) and 2.0 (0.8), respectively. Each had annual check-ups over 4 years. Short-term within-person variations of TC, LDL, HDL, TC/HDL, and LDL/HDL were 0.12 (coefficient of variation [CV] 6.4%), 0.08 (CV 9.4%), 0.02 (CV 8.0%) mmol2/L2, 0.08 (CV 7.9%), and 0.05 (CV 10.6%), respectively. The ratio of signal-to-noise at 3 years was largest for TC/HDL (1.6), followed by LDL/HDL (1.5), LDL (0.99), TC (0.8), and HDL (0.7), suggesting that cholesterol ratios are more sensitive re-screening measures.
Conclusions: The signal-to-noise ratios of standard single lipid measures (TC, LDL, and HDL) are weak over 3 years, and decisions based on these measures are potentially misleading. The ratios, TC/HDL and LDL/HDL, seem to be better measures for monitoring assessments. The lipid re-screening interval should be >3 years for those not taking cholesterol-lowering drugs.
Perspective: The results support the use of TC/HDL as the preferred lipid parameter for risk stratification, but are not generalizable. This Japanese cohort had a low BMI and low-risk lipid profile. The degree to which increasing BMI and triglycerides would alter the conclusion is not known, but may be considerable. The ratio of LDL to HDL needs to be obtained fasting, and in most cohort studies, has less ability than the TC/HDL to discriminate risk of cardiovascular events. Melvyn Rubenfire, M.D., F.A.C.C.
Title: Gadolinium-Enhanced Magnetic Resonance Angiography for Pulmonary Embolism: A Multicenter Prospective Study (PIOPED III)
Topic: Noninvasive Cardiology
Date Posted: 4/21/2010
Author(s): Stein PD, Chenevert TL, Fowler SE, et al., on behalf of the PIOPED III (Prospective Investigation of Pulmonary Embolism Diagnosis III) Investigators.
Citation: Ann Intern Med 2010;152:434-443.
Clinical Trial: No
Related Resources
Trial: Prospective Investigation of Pulmonary Embolism Diagnosis Study (PIOPED)
Study Question: What is the accuracy of gadolinium-enhanced magnetic resonance angiography, with or without magnetic resonance venography, for diagnosing pulmonary embolism?
Methods: In a prospective, multicenter study performed between April 2006 and September 2008, 371 adult patients at seven hospitals evaluated for pulmonary embolism were studied. Independently read magnetic resonance imaging was compared with the reference standard for diagnosis. (The reference standard used various tests, including computed tomographic angiography and venography, ventilation–perfusion lung scan, venous ultrasonography, D-dimer assay, and clinical assessment.)
Results: Magnetic resonance angiography, averaged across centers, was technically inadequate in 92 of 371 (25%) patients; the proportion of technically inadequate images ranged from 11% to 52% at various centers. Including patients with technically inadequate images, magnetic resonance angiography identified 59 of 104 (57%) patients with pulmonary embolism. Technically adequate magnetic resonance angiography had a sensitivity of 78% and a specificity of 99%. Technically adequate magnetic resonance angiography and venography had a sensitivity of 92% and a specificity of 96%, but 52% of patients (194 of 370) had technically inadequate results. Of note, a high proportion of patients with suspected embolism was not eligible or declined to participate.
Conclusions: The authors concluded that magnetic resonance pulmonary angiography should be considered only at centers that routinely perform it well, and only for patients for whom standard tests are contraindicated. In patients with technically adequate images, combined magnetic resonance pulmonary angiography and magnetic resonance venography have a higher sensitivity than does magnetic resonance pulmonary angiography alone, but it is more difficult to obtain technically adequate images with the two procedures.
Perspective: This is a realistic look at the application of a newer diagnostic imaging tool to a common clinical problem that has good (albeit imperfect) existing methods for diagnosis. The important strengths of magnetic resonance imaging were countered in this study by technically inadequate images in many patients who underwent the test, and by a substantial number of patients who––in this clinical setting––were ineligible for, or who declined to have the test. David S. Bach, M.D., F.A.C.C.