Non-fasting specimens are now acceptable Fasting specimens have traditionally been used for the formal assessment of lipid status (total, LDL and HDL cholesterol and triglycerides). In 2016, the European Atherosclerosis Society and the European Federation of Clinical Chemistry and Laboratory Medicine released a joint consensus statement that recommends the routine use of non-fasting specimens for the assessment of lipid status.² Large population-based studies were reviewed which showed that for most subjects the changes in plasma lipids and lipoproteins values following food intake were not clinically significant. Maximal mean changes at 1–6 hours after habitual meals were found to be: +0.3 mmol/L for triglycerides; -0.2 mmol/L for total cholesterol; -0.2 mmol/L for LDL cholesterol; -0.2 mmol/L for calculated non-HDL cholesterol and no change for HDL cholesterol. Additionally, studies have found similar or sometimes superior cardiovascular disease risk associations for non-fasting compared with fasting lipid test results. There have also been large clinical trials of statin therapy, monitoring the efficacy of treatment using non-fasting lipid measurements. Overall, the evidence suggests that non-fasting specimens are highly effective in assessing cardiovascular disease risk and treatment responses.

Non-HDL cholesterol as a risk predictor

In the 2016 European joint consensus statement² and in previously published guidelines and recommendations, the clinical utility of non-HDL cholesterol (calculated from total cholesterol minus HDL cholesterol) has been noted as a predictor of cardiovascular disease risk. Moreover, this marker has been found to be more predictive of cardiovascular risk when determined in a non-fasting specimen.

What this means for your patients

The assessment of lipid status with a non-fasting specimen has the following benefits:

• No patient preparation is required, thereby reducing non-compliance
• Greater convenience with attendance for specimen collection at any time
• Reports are available for earlier review instead of potential delays associated with obtaining fasting results

Indications for repeat testing or a fasting specimen collection

For some patients, lipid testing on more than one occasion may be necessary in order to establish their baseline lipid status. It is also important to note that an assessment of lipid status carried out in the presence of any intercurrent illness may not be valid. Conditions for which a fasting specimen collection is recommended² include:

• Non-fasting triglyceride >5.0 mmol/L
• Known hypertriglyceridaemia followed in a lipid clinic
• Recovering from hypertriglyceridaemic pancreatitis
• Starting medications that may cause severe hypertriglyceridaemia (e.g., steroid, oestrogen, retinoid acid therapy)
• Additional laboratory tests are requested that require fasting or morning specimens (e.g., fasting glucose, therapeutic drug monitoring)

Lipid reference limits and target levels for treatment are under review

The chemical pathology community in Australia is currently reviewing all relevant publications in order to implement a consensus approach to reporting and interpreting lipid results. This includes the guidelines for management of absolute cardiovascular disease risk developed by the National Vascular Disease Prevention Alliance (NVDPA).³

Further information

• Absolute cardiovascular disease risk calculator is available atwww.cvdcheck.org.au
• If familial hypercholesterolaemia is suspected, e.g. LDL cholesterol persistently above 5.0 mmol/L in adults, then advice about diagnosis and management is available at www.athero.org.au/fh

References

1. Rifai N, et al. Non-fasting Sample for the Determination of Routine Lipid Profile: Is It an Idea Whose Time Has Come? ClinChem 2016;62: 428-35.
2. Nordestgaard BG, et al. Fasting Is Not Routinely Required for Determination of a Lipid Profile: Clinical and Laboratory Implications Including Flagging at Desirable Concentration Cutpoints -A Joint Consensus Statement from the European Atherosclerosis Society and European Federation of Clinical Chemistry and Laboratory Medicine. Clin Chem 2016;62: 930-46.
3. National Vascular Disease Prevention Alliance, Absolute cardiovascular disease management, Quick reference guide for health professionals

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General Practice Pathology is a new fortnightly column each authored by an Australian expert pathologist on a topic of particular relevance and interest to practising GPs. The authors provide this editorial, free of charge as part of an educational initiative developed and coordinated by Sonic Pathology.