Internal Quality Control of Radioimmunoassays

Abstract

A modified cumulative sum technique has been applied to radioimmunoassay quality control data. The method is approximately 50% more efficient in detecting systematic changes in the mean and variance of quality control values for plasma samples than more widely used conventional methods. The salient features of the technique have been restricted to changes in the mean quality control value of a plasma pool, but potential applications to changes in variance and as a diagnostic aid to problems in radioimmunoassay have been evaluated. The method is independent of computing facilities and statistical expertise since all computations have been presented in the form of a nomogram and thus can be used by technicians at the bench.

Exploitation des contrôles de qualité

“…Cette méthode serait deux fois plus puissante pour détec-ter des changements systématiques de la moyenne et de la variance que les méthodes habituelles [4].…”

A Simple Robust Assay for Testosterone in Male Plasma Using an 125I-Radioligand and a Solid-Phase Separation Technique

“…PRECISION Three plasma pools of high, medium, and low testosterone concentration were established. Ten aliquots were assayed, and these data were used to assess intra-assay variation (Table 2) and to establish an initial value for the use of the cumulative sum (CUSUM) technique for quality control (Kemp et al, 1978). The pools were then used as quality 100 Fig.…”

Internal Quality Control of Radioimmunoassays: Monitoring of Error

“…Although certain quality control procedures are well known (Wetherill, 1969;Sarkadi & Vincze, 1974) and used for radio¬ immunoassays (Rodbard, Rayford & Ross, 1970;Challand «ft Chard, 1973;Rodbard, 1974;McDonagh, Munson «ft Rodbard, 1977), advances in control theory (Kemp, 1967;Rowlands, 1976) have now enabled more efficient quality control methods to be developed (Kemp, Nix, Wilson «ft Griffiths, 1978), based on the cumulative sum (CUSUM) technique. The need for monitoring the standard error associated with replicate determinations of the hormone concentration of an internal quality control plasma pool between successive batches of assays is generally appreciated intuitively, but few techniques are currently used to control this aspect of a radioimmunoassay (Challand & Chard, 1973;McDonagh et al 1977;Wilson, Nix, Kemp & Griffiths, 1977).…”

“…It is appropriate to state that efficiency can be achieved by selecting a quality control technique which is sensitive to changes in the value of the parameter being controlled such as the mean or assay error. In addition, where cumulative sum techniques are used to assist quality control, V-mask parameters (Barnard, 1959;Ewan «ft Kemp, 1960;Kemp, 1961;Duncan, 1974;Kemp et al 1978) such as the lead distance, d, and the half angle, , should be chosen to maximize the sensitivity of the technique for a given control statistic. Finally, it is important to use a control statistic which is most sensitive to changes in assay performance.…”