Fasting vs Nonfasting Plasma Homocysteine Concentrations for Diagnosis of Hyperhomocysteinemia

摘要

Hyperhomocysteinemia, a risk factor for cardiovascular and thrombotic disease, pregnancy complications, and cognitive disorders, is defined as a fasting plasma total Hcy (tHcy) above a chosen cutoff value (1)(2). Reducing both the analytical and biological variation may add to the diagnostic value of any test. tHcy analytical variation (CVa) is method-dependent and ranges from 2.7% to 4.9% for fluorescence polarization immunoassays and from 2.5% to 14% for HPLC assays (3). The reported biological variations for tHcy under fasting or otherwise standardized conditions include 20–34% interindividual variation (CVg) and 7–11% (with a single extreme of 15–17%) intraindividual variation (CVi) (4)(5)(6)(7)(8)(9). Because of the short-term influence of meals, e.g., protein, on CVi (10), it is generally recommended that blood samples be collected under fasting or otherwise meal-standardized conditions. The influence of protein intake on between-day CVi is, however, unknown. The necessity for fasting has been questioned because fasting and nonfasting tHcy concentrations and reference values, as well as fasting and postprandial short-term CVi and CVg values, are similar (11)(12).We investigated whether tHcy concentrations and variations under nonfasting conditions differ from those under fasting conditions. For this we calculated tHcy biological variation from samples taken at different clock times during a single day and during 3 weeks.We studied 16 apparently healthy individuals [8 men and 8 women; median (range) age, 44 (25–58) years]. Our study design is illustrated in Fig. 1A? . Six blood samples were taken from all participants on Monday of week 1. A standardized breakfast (0815 in the morning) and lunch (1215) and a dinner (1730–1800) of unrestricted composition and quantity were provided during the day. Participants documented food and beverage intake on Monday and …