The biochemical investigation of cases of hypoglycaemia: an assessment of the clinical effectiveness of analytical services.

AIM: To assess the extent to which biochemical analytical services contribute to the diagnosis and management of clinical cases of hypoglycaemia. METHODS: All cases of confirmed hypoglycaemia, referred during a six month period, were included in the survey. Questionnaires were sent to each referring laboratory requesting information on the clinical progress and current status of the patient. RESULTS: The level of influence exerted by analytical data was assigned in each case and those with similar outcomes combined. Identifiable case groups were: (1) Results not recorded in the patients' notes (15.7%). (2) Inappropriate requesting of insulin and C peptide measurements in cases of diabetes (11.4%). (3) Patient died soon after investigation (20.0%). (4) Patient recovered spontaneously (17.1%). (5) Patient received effective medical or surgical treatment (12.9%). (6) Patient awaiting or not requiring pathology based treatment (31.4%). (7) Inconclusive outcome prompting further investigation (5.7%). CONCLUSIONS: Within the timescale of the survey (approximately 12 months), positive progress had been made towards diagnosis and subsequent treatment in only 10% of cases. Another 30% were either awaiting some form of treatment or further diagnostic tests. The remaining 60% did not appear to benefit in any way from the biochemical investigations.

Assessment of the suitability of commercially available SpA affinity solid phases for the purification of murine monoclonal antibodies at process scale.

Eight commercially available staphylococcal protein A (SpA) affinity chromatography solid phases were evaluated in order to establish their potential for the large-scale purification of a murine monoclonal antibody (MAb, mIgG1). The antibody was produced in-house, serum-free, in a hollow fibre bioreactor. Solid phases were tested for the effects of salt concentration, pH, and the presence of MAb on ligand leakage and flow rate. These effects were compared using the solid phases in stirred-tank (roller-mixing) and flow-through (packed-bed) modes of operation. Ligand leakage in the absence of MAb was generally at its lowest when the solid phases were used in a flow-through mode. In this mode of operation increasing the inorganic salt concentration and pH of the washing/adsorption buffer from 150 mM at pH 8.6, to 3 M at pH 8.9, typically produced a 10% increase in MAb capacity of the solid phases (20% for Sepharose CL-4B). However, contamination of the purified antibodies was also greatly increased due to an elevated level of background ligand leakage from the matrices. Residual contaminating levels of SpA in affinity purified MAbs were lowest with a low salt (NaCl, 150 mM) glycine (1 M) adsorption/washing buffer. Maximal antibody capacity was achieved for all matrices on frontal analysis (breakthrough curves), as opposed to a pulse mode of use. The largest capacity was found for Prosep A 'high capacity' (12-15 mg/ml column volume), where capacity approached its experimentally determined theoretical capacity (C/Co = 0.5) regardless of its mode of use. The relatively high MAb capacity of Prosep A 'high capacity' was further reflected in a superior dynamic isotherm. Frontal analysis, however, generally resulted in a greater SpA contamination of the purified MAbs. Under these conditions the lowest levels of SpA contamination were found for the Prosep A 'high capacity', and Repligen solid phases (12 ppm) on purifying 12.8 and 4.3 mg of MAb respectively. For the large scale downstream processing of a MAb for therapeutic applications, Prosep A 'high capacity', would appear to be the most appropriate of the solid phases tested.

Essential considerations in the provision of near-patient testing facilities.

(1) Near-patient testing (NPT) is both practicable and in some situations desirable. (2) Like all new technologies its apparent simplicity often belies its complexity and masks the need for attention to detail in order to achieve optimum effects and avoid disasters. (3) Though technically unskilled individuals are capable of using it, they must undergo training in the elements of safety, sample collection, quality control, quantitation and documentation before being authorized to provide analytical services for patients. (4) Health Authorities should be encouraged to adopt a policy of integration of NPT and clinical laboratory services in order to reduce unplanned use and abuse of NPT facilities which is not only wasteful and divisive, but also dangerous. This has recently been emphasized in the United Kingdom by the release of a Hazard Notice (HN (Hazard) (87) 13) by the Department of Health and Social Security. The experienced clinical biochemist will, by virtue of training and experience, usually be the most suitable person in a Health District to advise on many of the issues involved in NPT. It should therefore, be the responsibility of laboratory staff to work with management, clinical, and nursing staff to: choose appropriate sites for the various levels of service to be provided to meet a clinical need; select the equipment and reagents to be employed; provide training in the use of the apparatus, quality control and safety; authorize accredited users and oversee the quality assurance programme. (5) Laboratory staff will need to involve themselves closely in the financial implications of NPT both for the laboratory's benefit and that of clinical practice within the hospital and/or community as a whole.

Determination of total bile acids in serum. A comparison of a radioimmunoassay with an enzymatic-fluorimetric method.

A solid phase radioimmunoassay kit method for total conjugated bile acids has been compared to an enzymatic fluorimetric method for total serum bile acids. The methods were compared with respect to: precision, cross-reactivity (molar equivalence) of different bile salts, recovery of different bile salts from serum, the reference range for a healthy population, linearity, coefficient of correlation, diagnostic effectiveness, cost and ease of assay. Both assays seemed equally capable of predicting the presence or absence of liver disease. Radioimmunoassay had little advantage over the enzymatic-fluorimetric method. Its relative ease was far outweighed by its greater cost and poorer analytical performance.