Clinical biochemistry reference interval is generally calculated as 2.5th and 97.5th percentile of the distribution among health population. The accuracy of reference range has implication in disease diagnosis, assessment of disease severity and treatment monitoring. Both International Federation of Clinical Chemistry (IFCC) and Clinical and Laboratory Standards Institute (CLSI) recommend derivation of regional reference limits owing to variation in geography, diet pattern, climate and genetic characteristics. Liver enzyme levels are tested to interpret the extent of damage to the liver or abnormal bile flow. Liver function test are becoming a routine diagnosis and part of blood biochemistry tests. However, the abnormal readings pose clinical challenge to the physicians and form a basis for further diagnostics tests, some of which may be cost-intensive. Therefore, the reference range becomes very critical for accuracy in diagnosis. Reliable interpretation of liver biochemical abnormality depends on the establishment of the normal range and the application of most suitable reference range.
Reference range limits are variable with respect to the laboratory, age of the study population and geographical area of inhabitation. It is possible that patients of liver diseases may exhibit normal levels and asymptomatic individuals may exhibit abnormal levels. In this context importance of normal ranges and establishment of reference ranges for serum biochemistry attains even greater significance. Use of reference range from distant populations could potentially lead to misdiagnosis, inappropriate patient management and unjustified use of resources. Based on biochemical readings of eight liver function parameters in healthy children (n=768) aged 1 to 17 years, Kainyu and team from Kenya have reported establishment of local reference ranges for liver biochemical parameters for Kenyan children. The study revealed that serum bilirubin, total protein and albumin were higher than Caucasian children while ALP had shorter reference range. This unique attempt is of great significance as reference ranges were not available for geographical population of Meru County, Kenya and the local physicians were relying on data from Caucasian populations, that too of adult population. Population specific and age specific reference range have immense clinical relevance in terms of accurate diagnosis and precise treatment. The authors have further emphasized on developing more such local reference ranges to complement the normal range values in diagnosis based on liver parameters.