Reference values

Reference value is a term used in medicine to denote a laboratory value used as a reference for values obtained by laboratory examinations of patients or samples (blood, urine or other materials) collected from patients.

An important step in the interpretation of data from medical laboratory examinations is comparison with relevant reference data. For example, when the doctor interpretes a fasting patient's glucose concentration in blood he might ask the following questions: What are the glucose concenctrations usually found in healthy individuals? Or in diabetic patients? A patient's laboratory result simply is not medically useful if appropriate data for comparison are lacking.

An earlier term, normal values, has been abandoned because of many confusing connotations of "normal" and it has been replaced by the more neutral term reference values.

Most medical laboratories provide reference data for all examinations that may be ordered, commonly in the form of reference intervals for healthy individuals. A 95% reference interval usually is bounded by two limiting values and contains 95% of the values found in healthy individuals. Since laboratory results often are dependent on sex and age, it is often necessary to have separate reference intervals for the two sexes and/or for different age groups. A laboratory result located outside the corresponding health-related reference interval does not necessarily imply that the individual is diseased or at risk.

The International Federation of Clinical Chemistry (IFCC) has published a recommendation in six parts on reference values. This series of publications deals with the scientific basis of reference values and related concepts and with the establishment of reliable reference data. Many national and regional recommendations, usually based on that of IFCC, have also been published.