Polymerase chain reaction analysis of allele frequency and loss at the Harvey ras locus in myeloid malignancies.

The hypothesis that 'rare' variable number tandem repeat (VNTR) alleles of the Harvey ras (Ha-ras) locus are an inherited predisposing factor in myeloid malignancies has been evaluated. We describe an application of the polymerase chain reaction (PCR) which amplifies the VNTR region at the Ha-ras locus and offers a number of advantages over conventional Southern analysis. Ha-ras VNTR genotypes were assigned to 57 normal subjects, 46 patients with acute myeloid leukaemia (AML), 26 with myelodysplastic syndrome (MDS) and 49 with chronic granulocytic leukaemia (CGL). By comparison with previous reports we found significantly higher frequencies of rare alleles (20.2%) in our normal subjects of whom more than 35% had at least one 'rare' allele. The frequencies of rare alleles in the patient groups was not significantly different from the normal group (chi 2 = 0.54, p = 0.91). In studies of constitutional and leukaemic DNA from patients with AML, we found that allelic loss at the Ha-ras locus was not a common phenomenon. The improved resolution achievable with PCR compared with Southern analysis was demonstrated by the inability of Southern analysis to resolve six out of 34 PCR heterozygotes. We therefore suggest that previous studies showing linkage between rare Ha-ras alleles and susceptibility to malignancy should be reevaluated using our sensitive PCR technique.

Continuous assessment of performance in External Quality Assessment Schemes.

A simple, standardised procedure was used for processing data from External Quality Assessment Schemes and for producing performance charts. A graphic presentation of cumulative performance is generated for each test, using an integrated software package to display results in a standardised format. This permits interpretation of satisfactory and poor performances and facilitates identification of "outlying" results. Although most results are recorded as Deviation Indices, the system is flexible and can be used to present other performance variables, such as Percentage Deviations and relevant textual information relating to interpretative assessments. It is therefore readily adaptable for use by other pathology disciplines.

A proposal for further standardization of red blood cell glucose 6-phosphate dehydrogenase determinations.

A number of factors were identified which influence the determination of red blood cell glucose 6-phosphate dehydrogenase (G6PD). White blood cells were effectively removed from whole blood by filtration, resulting in a mean reduction of G6PD activity of greater than 1.0 U/g Hb. Optimal enzyme activity was found using haemolysates with a Hb concentration in the range 0.4-1.2 g/dl. At a constant temperature of 30 degrees C, maximum linear rate of activity was achieved between the 10th and 20th min after initiation of the reaction. As a result of these findings, modifications to standardize the assay system were introduced. The new method exhibits excellent precision (CV less than 2.0%) with normal samples, and 95% reference ranges of 7.00-11.15 U/g Hb for adult females and 7.05-10.75 U/g Hb for adult males.

Microcomputer data handling for the Phoenix system.

A modified Phoenix data processing system has been introduced into the laboratories at the Manchester Royal Infirmary. Specifications for the design and installation of microcomputers to link automated instruments to this host computer are described. The operation and data manipulation facilities of the microcomputer are included. It is concluded that these devices aid the management of data within the department and improve the quality of service.