SUMMARYHepatitis C virus (HCV) infection has been implicated in the pathogenesis of mixed cryoglobulinaemia. Several studies have shown the presence of anti-HCV antibodies and HCV-RNA in both sera and cryoglobulins of such patients. However, the prevalence and clinical significance of cryoglobulins remain uncertain in patients with chronic HCV infection. We have studied 113 consecutive patients referred for assessment because of the presence of anti-HCV antibody in serum for the presence of cryoglobulinaemia and ascertained their clinical relevance and immunochemical properties. Twentyone of 113 (19%) had detectable cryoglobulins with a mean protein concentration of 0 . 38 g/l (range 0 . 15-3 . 34 g/l). Most of these patients were asymptomatic. The cryoglobulins were of type III in 19 (91%) and of type II in two patients (9%). The latter two patients had the highest concentration of cryoglobulins, subnormal C4 and C1q levels suggesting classical pathway activation and vasculitis with renal impairment. The cryoglobulin IgG subclasses were mainly IgG1 and IgG3. HCV-RNA was detected more frequently in the sera of cryoglobulin-positive patients than in cryoglobulin-negative patients. This study showed that mixed cryoglobulinaemia is common in chronic HCV infection, and is predominantly type III. Evidence of systemic or renal disease was rare except in those with type II cryoglobulinaemia, and this may reflect either the concentration of the cryoprecipitate or the presence of a monoclonal complement-activating IgM paraprotein. The detection of HCV-RNA in the majority of the cryoprecipitates further supports the important role of HCV in the etiopathogenesis of essential mixed cryoglobulinaemia, although the mechanism is at present unclear.

Fourier-transform infrared transmission spectroscopy has been used for the determination of glucose concentration in whole blood samples from 28 patients. A 4-vector partial least-squares calibration model, using the spectral range 950-1200 cm(-1), yielded a standard-error-of-prediction of 0.59 mM for an independent test set. For blood samples from a single patient, we found that the glucose concentration was proportional to the difference between the values of the second derivative spectrum at 1082 cm(-1) and 1093 cm(-1). This indicates that spectroscopy at these two specific wavenumbers alone could be used to determine the glucose concentration in blood plasma samples from a single patient, with a prediction error of 0.95 mM.

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Fourier-transform infrared(FTIR) transmission spectroscopy has beenused for the determination of glucoseconcentrations in whole blood samples fromtwenty-eight patients. A four-vectorpartial least squares calibration model,using the spectral range 950-1200 cm(-1),yielded a standard error of prediction of0.59 mM for an independent test set. Forblood samples from a single patient, wefound that the glucose concentration wasproportional to the difference between thevalues of the second derivative spectrum at1082 cm(-1) and 1093 cm(-1), suggestingthat these two specific wavelengths can beused for determining glucose concentrationsin blood.

A simple method for collecting capillary blood for measurement of glycosylated haemoglobin (HbA1c) was developed that allows samples to be obtained at home and then mailed to the laboratory 2 weeks before a hospital visit. A single drop of blood is collected into a 2 ml plastic tube and sent for HbA1c assay on the Diamat HPLC system which has inter- and intra-assay coefficients of variation < 2.6 and < 1.2%, respectively. Results of simultaneously obtained venous and capillary samples in 32 diabetic children agreed well with each other. A separate study of 25 patients was performed to determine whether transport conditions affected the samples. Posted samples were compared with venous samples; again the values were in good agreement. This method is now used routinely in the diabetic clinic. Its value was determined by questionnaire in 40 children with age range 4-17 years. No family experienced difficulty collecting samples and all samples received were suitable for analysis. Children preferred this method to blood collection in the clinic as they felt it was less traumatic and more convenient. Seventy-nine percent of them understood its value in the long-term control of diabetes. In 40.5% of visits changes to management were made at the clinic due to the availability of the results.