Dear Jonathan, What we by convention decide is without uncertainty. We eventually decide that the reference values are the limits of a reference interval which may have been obtained in any acceptable manner. The reference values are given without uncertainty. It is not until we measure them that the uncertainty develops. It is the same with h. As defined it has no uncertainty but if we measure it the result has an uncertainty associated. Would you agree? Beset regards, Anders Anders Kallner, MD, PhD Assoc Prof (R) Karolinska University Hospital SE 176 71 Stockholm, SWEDEN Phone: +46 8 51774943 [log in to unmask] När du skickar e-post till Karolinska Institutet (KI) innebär detta att KI kommer att behandla dina personuppgifter. Här finns information om hur KI behandlar personuppgifter<https://ki.se/medarbetare/integritetsskyddspolicy>. Sending email to Karolinska Institutet (KI) will result in KI processing your personal data. You can read more about KI’s processing of personal data here<https://ki.se/en/staff/data-protection-policy>. ------ACB discussion List Information-------- This is an open discussion list for the academic and clinical community working in clinical biochemistry. Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual who posts and they are solely responsible for all message content. The ACB does not monitor posts. ACB Web Site http://www.acb.org.uk Green Laboratories Work http://www.laboratorymedicine.nhs.uk List Archives http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html List Instructions (How to leave etc.) http://www.jiscmail.ac.uk/