Derivation of reference ranges in clinical chemistry from patient population

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Derivation of reference ranges in clinical chemistry from patient population


Author: Lo, Wai-shan
Title: Derivation of reference ranges in clinical chemistry from patient population
Degree: M.Sc.
Year: 1998
Subject: Clinical chemistry -- Statistical methods
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Pages: x, 120 leaves : ill. ; 30 cm
Language: English
InnoPac Record:
Abstract: In an attempt to demonstrate a rapid and economical approach to derive reference intervals, the relative modal frequency(RMF) algorithm was developed. It was a new algorithm applied on patient data in the Prince of Wales hospital. No gaussian assumption was imposed on the algorithm. A power transformation of the central portion of the patient data into a Gaussian distribution was done with the help of a modal Q-Q plot. About 90000 data of different analytes were downloaded from the hospital host computer per year. Three years(1992, 1993, 1994) data were analyzed. Clinical analytes including sodium, albumin, total protein, creatinine, alkaline phosphatase and alanine aminotransferase(ALT) were studied. Sodium was known to be Gaussian distributed; albumin and total protein were left-skewed distributed; while creatinine, alkaline phosphate and ALT were right-skewed distributed. Patient data were selected on Hong Kong Identity number basis to avoid duplicate results from the same patient, about two-third of data were discarded. To eliminate the requirement for encountering the effect of treatments on analyte concentrations, first analyte result from each patient after admission was selected. Age and sex subgroups were subdivided for creatinine and alkaline phosphatase. For each analyte, the consistence of the reference ranges upon changes of sample size were studied, and the minimum sample size required for a steady reference range was established by meta-analysis. It was found that 8000 selected data would be sufficient for the selected analytes to develop a steady reference range, and it took about 4 months to collect these data. The validity of the algorithm were tested by comparing the derived reference ranges with those from the Bhattacharya's method. The algorithm worked as efficient as Bhattacharya's method on Gaussian analyte, sodium; and worked better on skewed analyte, albumin. The algorithm was verified by comparing with literature values (Tietz, 1987) and reference values established from the Lek Yuen Project (To, 1988) done by PWH in 1984. Most of the reference ranges developed by the RMF algorithm are comparable to those of the published literature and the Lek Yuen data. Discrepancies found may due to incomplete elimination of abnormal data, or physiological and biological variations between patient and healthy subjects. Different sex and age distributions between patient population and reference population may also result in different reference ranges. The RMF is an indirect method, which has the problem of lacking patient detail characteristics. However, under the assumption that patient are normal in most aspects, indirect methods, including the RMF algorithm, have no problem to work on routine biochemical analytes.

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