Fasting Duration and Differences Across Routine Laboratory Tests

Abstract
Importance Fasting before blood collection is widely practiced to reduce preanalytical variability, yet whether fasting-related differences are clinically meaningful across a broad panel of routine analytes has not been systematically evaluated using clinical data.

Objective To evaluate whether fasting duration is associated with routine laboratory test results and whether observed differences exceed established analytical performance specifications (APS).

Design, Setting, and Participants Retrospective single-center cross-sectional study using laboratory information system data collected between February 2021 and December 2023 from a single 670-bed secondary-care university hospital in the Seoul metropolitan area, Republic of Korea. All samples were drawn from outpatients at the institution’s central phlebotomy unit. Participants were adult outpatients (≥18 years) with documented fasting duration. Data were analyzed from January 1, 2024, to July 24, 2026.

Exposure Fasting duration derived from the time elapsed between the patient’s last meal and blood collection, categorized as less than 8 hours, 8 to 12 hours, and more than 12 hours.

Main Outcomes and Measures Adjusted means across fasting groups were estimated using linear mixed-effects models with patient-level random intercepts, adjusting for age, sex, and department. Paired within-person analyses among repeatedly tested patients were performed to minimize between-patient confounding. Differences were compared with the European Federation of Clinical Chemistry and Laboratory Medicine biological variation–based total allowable error. Postprandial trends within the subgroup fasting less than 8 hours were assessed at 30-minute intervals.

Results The final dataset comprised 9 755 547 test results from 101 148 patients across 372 test items. Between-group comparisons identified APS-exceeding differences for 27 analytes. However, only 10 were confirmed in paired within-person analyses, suggesting confounding. Glucose (10.8%), triglycerides (20.1%), γ-glutamyl transferase (14.8%), and lipase (36.4%) were higher with less than 8 hours fasting. No analyte exceeded APS between the 8- to 12-hour and more than 12-hour groups. Within the less than 8-hour subgroup, glucose and lactate decreased significantly with increasing fasting duration, whereas lipid concentrations showed no significant linear trend.

Conclusions and Relevance This cross-sectional study found that fasting duration was associated with differences exceeding analytical performance specifications for only a few analytes, mainly glucose, triglycerides, γ-glutamyl transferase, and lipase. No estimable within-person difference between the 8- to 12-hour and more than 12-hour groups exceeded an available APS. These findings support analyte-specific rather than uniform fasting requirements.

Author/s:

Sunghwan Shin, Sollip Kim, Shinae Yu, Soo Jin Yoo, Kuenyoul Park, Jeonghyun Chang, Tae-Hyun Um, Chong Rae Cho, Dong Hee Whang

Association of Nonfasting vs Fasting Lipid Levels With Risk of Major Coronary Events in the Anglo-Scandinavian Cardiac Outcomes Trial–Lipid Lowering Arm

Tracy Ashby — Thu, 30 May 2019 05:00:00 +0000

Date Added:

May 30, 2019

Journal/Publication:

JAMA

Publisher:

American Medical Association

Publication Date:

May 28, 2019

URL:

Association of Nonfasting vs Fasting Lipid Levels With Risk of Major Coronary Events in the Anglo-Scandinavian Cardiac Outcomes Trial–Lipid Lowering Arm

Type:

Clinical Research Results

Format:

Article

DOI (1):

10.1001/jamainternmed.2019.0392

Keywords

PMID (1):

31135812

MeSH

fasting

Hydroxymethylglutaryl-CoA Reductase Inhibitors

cardiovascular diseases

risk factors

cholesterol, LDL

myocardial infarction

coronary disease

For purposes of risk assessment and decisions about risk reduction, non-fasting lipid levels seem to be fine (no real need to obtain fasting lipid levels). James W. Mold, MD, MPH

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IMPORTANCE:

Recent guidelines have recommended nonfasting for routine testing of lipid levels based on comparisons of nonfasting and fasting populations. However, no previous study has examined the association of cardiovascular outcomes with fasting vs nonfasting lipid levels measured in the same individuals.

OBJECTIVE:

To compare the association of nonfasting and fasting lipid levels with prospectively ascertained coronary and vascular outcomes and to evaluate whether a strategy of using nonfasting instead of fasting lipid level measurement would result in misclassification of risk for individuals undergoing evaluation for initiation of statin therapy.

DESIGN, SETTING, AND PARTICIPANTS:

This post hoc prospective follow-up of a randomized clinical trial included 8270 of 10 305 participants from the Anglo-Scandinavian Cardiac Outcomes Trial-Lipid Lowering Arm (ASCOT-LLA) with nonfasting and fasting lipid levels measured 4 weeks apart (including 6855 participants with no prior vascular disease) (median follow-up, 3.3 years; interquartile range, 2.8-3.6 years). Data were collected from February 1, 1998, to December 31, 2002, and analyzed from February 1, 2016, to November 30, 2018. Multivariable Cox models, adjusted for cardiovascular risk factors, were calculated for 40-mg/dL (1-mmol/L) higher values of nonfasting and fasting lipids.

MAIN OUTCOMES AND MEASURES:

The trial's primary end point consisted of major coronary events (nonfatal myocardial infarction [MI] and fatal coronary heart disease [212 events]). Secondary analyses examined atherosclerotic cardiovascular disease (ASCVD) events (including MI, stroke, and ASCVD death [351 events]).

RESULTS:

Among the 8270 participants (82.1% male; mean [SD] age, 63.4 [8.5] years), nonfasting samples had modestly higher triglyceride levels and similar cholesterol levels compared to fasting samples. Associations of nonfasting lipid levels with coronary events were similar to those for fasting lipid levels. For example, adjusted hazard ratios (HRs) per 40-mg/dL of low-density lipoprotein cholesterol were 1.32 (95% CI, 1.08-1.61; P = .007) for nonfasting levels and 1.28 (95% CI, 1.07-1.55; P = .008) for fasting levels. For the primary prevention group, adjusted HRs were 1.42 (95% CI, 1.13-1.78; P = .003) for nonfasting levels and 1.37 (95% CI, 1.11-1.69; P = .003) for fasting levels. Results were consistent by randomized treatment arm (atorvastatin calcium, 10 mg/d, or placebo) and similar for ASCVD events. Concordance of fasting and nonfasting lipid levels for classifying participants into appropriate ASCVD risk categories was high (94.8%).

CONCLUSIONS AND RELEVANCE:

Measurement of nonfasting and fasting lipid levels yields similar results in the same individuals for association with incident coronary and ASCVD events. These results suggest that routine measurement of nonfasting lipid levels may help facilitate ASCVD risk screening and treatment, including consideration of when to initiate statin therapy.

Author/s:

Mora, Samia, Chang, C. Lan, Moorthy, M. Vinayaga, Sever, Peter S.