How to define fasting in a biochemical setting

How to define fasting (in a biochemical setting) Mads Nybo Dept. of Clinical Biochemistry Rigshospitalet

How to define fasting l l l General aspects Scientific evidence for the need of fasting Definition in medical journals Definition at Dept. s of Clinical Biochemistry Conclusion (? )

Danish Medical Compendium, 15 th ed. l l l Fasting 10 -16 hours prior to sampling No explicit physical activity in the hours before sampling No smoking

Fasting variables l l Duration of fasting (6 -16 hours) Liquid intake (incl. coffee, tea and alcohol) Physical activity (strenous, moderate, resting time? ) Smoking

Literature search 98. 9% of all fasting samples (220. 898 analyses) were for lipid or glucose analysis (Odense University Hospital, 2003)

Literature search l Statland, Winkel & Bokelund in the 70’es l Alström T et al. SJCLI 1993 Renewed guidelines, stating that 1) only intake of water after 22 pm is allowed 2) physical activity must not be strenous the day before, and only limited (15 minutes by foot) at the day of sampling 3) only one drink of alcohol the day before sampling Not mentioned Smoking, amount of water, literature references

Literature search (extract) l Wide variety between fasting and noon sampling – l Smoking associated increase in e. g. adrenalin, cortisol, FFA – l l Triglycerides both in- and decrease described Most analyses normalised after 15 minutes of rest – l Increase in Triglycerides! Though not for strenous exercise, e. g. decrease in P-Glucose up to 12 hours after! 200 ml coffee can cause an 0. 5 mmol/L increase in PGlucose Significant decrease in P-Glucose 20 hours after

Fasting definition in medical journal Articles with fasting patients Welldefined fasting Insuff. definition Undefined Clinical Chemistry Clin Chem Lab Med 46 6. 5 23. 9 69. 6 53 3. 8 28. 3 67. 9 Scand J Clin Lab Invest 37 10. 8 18. 9 70. 3 Diabetes 201 9. 0 41. 2 49. 8

Questionnaire l l Questionnaire concerning fasting variables to elucidate the national definition 20 Dept. of Clinical Biochemistry Reply from 16 Very few comparable!

Fasting variable – Duration of fasting

Fasting variable – Alcohol intake

Fasting variable – Coffee intake l )

Fasting variable – Smoking

Conclusions l l l Fasting do influence the analysis results – especially Triglycerides and Glucose Lack of harmonisation of fasting in the literature and among Dept. s of Clinical Biochemistry This could indeed have clinical relevance (diagnostics, monitoring), and a united fasting definition is thus needed

Future aspects to be dealt with l l l Consensus on these aspects – a Nordic guideline? (Nordic Clinical Biochemistry regime? ) Information to the clinicians (no matter what the conclusions may be!) Scientific awareness on the aspect (e. g. in journals)

However … l Does a fasting person represent his normal self? ? l And should analysis not requiring fasting thus be preferred?