Application of R-charts to detection of random errors: a computer simulation study.

The application of R-charts to quality control in clinical chemistry was investigated. These charts are widely used in statistical process control and plot the range (ie the difference between the highest and the lowest values) of a set of controls. A set of five control serums was considered. A computer simulation program was developed for this investigation. It showed a power function that is remarkably insensitive to systematic errors. Consequently these charts may be a useful tool in discriminating between systematic and random errors, helping the trouble-shooting significantly, if used concurrently with Levey-Jennings' charts. Nevertheless, as several control samples are necessary, this technique is not cost-effective for short analytical runs.

Purification and properties of carboxylesterase B of Escherichia coli.

Carboxylesterase B produced by Escherichia coli was purified 1,350-fold with a recovery of 12% by successive gel filtrations, DEAE-trisacryl, phenyl-Sepharose chromatography and preparative electrophoresis. The purified enzyme was found to be homogeneous, as judged by a single precipitation line in Ouchterlony double diffusion in an experiment with homologous antiserum. The apparent molecular weight determined by gel filtration and the isoelectric point determined by electrofocusing were 57,000 and 4.6, respectively. Using acetate, propionate and butyrate esters of 1-naphtol, it was observed that elongation of the acyl carbon chain resulted in a progressive increase in velocity of ester hydrolysis. The apparent Km for 1-naphtyl acetate was found to be 0.25 mM. The enzyme was maximally active at pH 7.4 and was found to be unstable below pH 5. Hydrolytic activity was preserved after heat treatment for 30 min at 60 degrees C, but was abolished by heating for 10 min at 70 degrees C. The enzyme was strongly inhibited by low concentrations of di-isopropyl fluorophosphate. This suggested that a serine residue is required for catalytic activity. Esterase was unaffected by tosyl-L-lysin chloromethylketone, iodoacetamide, 4-hydroxy-mercuribenzoate and EDTA. Using antiserum against purified carboxylesterase B of E. coli, significant immunological cross-reactions were observed between this antigen and carboxylesterase B produced by Shigella flexneri, S. boydii and S. sonnei.

[Gamma-heavy chain disease with autoimmune abnormalities and peripheral neuropathy (author's transl)]. / Maladie des chaînes lourdes gamma avec auto-anticorps multiples et neuropathie périphérique.

The authors report the case of a 72 year old woman affected by gamma heavy chain disease in whom the heavy chain was detected in the serum and the urine as well. Further study of the paraprotein showed that it belonged to the gamma 1 subclass. This observation was unusual because of the presence of a 15 year-long peripheral neuropathy and the existence of various auto-antibodies, especially intrinsic factor antibody.