Point-of-care method for total white cell count: an evaluation of the HemoCue WBC device

Point-of-care testing (POCT) is becoming an important adjunct to haematology laboratory practice. An important component of the blood count is the total white cell count (WBC). Previously, this required laborious microscopic cell counting, but it can now be performed by means of automation; however, in many under-resourced countries, costly automated counters are only available in very few central hospitals. Moreover, neither method is practical in most POCT situations. The HemoCue WBC has been developed as a simplified alternative method, consisting of a reagent pre-loaded disposable cuvette together with basic image analysis technology. This report describes an assessment of its utility. The WBC of 500 routine blood samples from the hospital were tested in parallel by the HemoCue WBC and by a reference analyser to assess accuracy and utility of the former. The tests included precision, linearity, type of blood sample and anticoagulant and potential interfering substances in blood specimens. In the tests for accuracy, 192 of the 200 showed percentage difference from the NEQAS reference of <10% whilst the remaining eight samples differed by <12%, thus meeting the requirements of Clinical laboratory improvement amendments (CLIA)-88 regulations. Of the samples tested with potential interfering substances only those with >2% normoblasts or reticulocytosis showed significant differences from the reference measurements. The HemoCue WBC is reliable for WBC counts within the analytical range of 0.4-30.0 x 10(9)/l, except in samples where there are significant numbers of normoblasts or reticulocytes. It is simple to use and provides a valuable advance in the facilities available for POCT in haematology.

An analysis of relative costs and potential benefits of different policies for antenatal screening for beta thalassaemia trait and variant haemoglobins

AIMS

To investigate the costs and potential benefits of different policies for antenatal screening for haemoglobinopathies in two multiethnic London communities.

METHODS

1000 consecutive antenatal patient samples referred to each of two London teaching hospital laboratories for haemoglobinopathy testing were investigated using the standard procedures of the laboratory in question. When the standard procedures did not include high performance liquid chromatography (HPLC), this technique was added, in order to assess its diagnostic value and cost-effectiveness. A comparison was made between the costs and potential benefits of universal testing for variant haemoglobins and beta thalassaemia trait using HPLC and the costs and potential benefits of universal testing for variant haemoglobins and selective testing for beta thalassaemia trait using the mean cell haemoglobin (MCH) as a screening test and less automated techniques than HPLC for definitive diagnosis.

RESULTS

The costs of the two policies were found to be comparable, as the higher reagent/instrument costs of HPLC were offset by the lower labour costs. Universal testing of 2000 consecutive samples did not disclose any extra cases of beta thalassaemia trait which would not have been detected by universal screening and selective testing. However, six patients were found to have a haemoglobin A2 variant which can interfere with the diagnosis of beta thalassaemia trait.

CONCLUSIONS

The introduction of universal testing by HPLC into British laboratories could be cost neutral and has potential benefits. If a higher cost is accepted then the greater degree of automation could be used to release skilled staff for other tasks within the laboratory.

Candidate gene approach of familial morbid obesity: linkage analysis of the glucocorticoid receptor gene

BACKGROUND

Morbid obesity is a multifactorial disease, with a strong but almost unknown genetic component. Familial linkage studies using the candidate gene approach have been shown to be powerful tools for identifying susceptibility genes for inherited diseases.

AIM OF THE STUDY

We have investigated the role of the Glucocorticoid Receptor gene (GRL) in morbid obesity.

SUBJECTS

Eighty obese families were recruited through a multimedia campaign (42 families, sample 1) or from the department of nutrition of the Hotel Dieu hospital in Paris (38 families, sample 2).

METHODS

A multipoint linkage analysis with markers on chromosome 5q placed the GRL gene between D5S658 and D5S436 at genetic distances of 3.5 and 5 centimorgans, respectively. Using this map, we have chosen seven polymorphic microsatellite markers located in the vicinity of the GRL gene locus for sib pair linkage analysis. In addition to the obesity status, different quantitative phenotypes associated with obesity and insulin resistance were used for analysis.

RESULTS

In sample 1, the results show a tendency towards linkage between three markers (one bc/1 intragenic RFLP and two microsatellite markers) in the GRL region and obesity characterised by a BMI > 27. However, using this phenotype, we failed to replicate the results in the second set of families. When using a more precise phenotype (the individual coefficient of variation of the BMI compared to a sex and age matched French reference population (pop) defined as the Zscore (indBMI-popBMI/SD of popBMI), a tendency for linkage was found for one marker in sample 2 as well as in the whole sample. No linkage was found when using quantitative traits associated with obesity.

CONCLUSION

The GRL locus does not appear to be a major locus for obesity, but we cannot exclude that this gene or gene located nearby may have some minor effects on the obese phenotype or may be involved in some subtypes of obesity. Larger cohorts of families are probably necessary to improve the power of such linkage analysis in this heterogeneous disease.

Indication for linkage of the human OB gene region with extreme obesity

Obesity is one of the most significant risk factors for hypertension, coronary heart disease, and NIDDM (Frayn KN, Coppack SW: Insulin resistance, adipose tissue and coronary heart disease. Clin Sci 82:1-8, 1992; Kaplan NM: The deadly quartet: upper-body obesity, glucose intolerance, hypertriglyceridemia, and hypertension. Arch Intern Med 149:1514-1520, 1989). While family segregation, adoption, and twin studies have indicated that degree of adiposity has a significant genetic component (Stunkard AJ, Harris JR, Pedersen NL, McClearn GE: The body-mass index of twins who have been reared apart. N Engl J Med 322:1483-1487, 1990; Bouchard C, Despres J-P, Mauriege P: Genetic and nongenetic determinants of regional fat distribution. Endocr Rev 14:72-93, 1993), the genes and predisposing mutations remain poorly understood. This is in contrast to several well-defined genetic models for obesity in rodents, particularly the mouse obese (ob) gene, in which loss-of-function mutations cause severe obesity. Recent studies have demonstrated a substantial reduction in body fat when recombinant ob protein (leptin) is administered to mice. To test the relevance of these observations to human obesity, the location of the human homologue (OB) was established by radiation hybrid mapping and eight microsatellite markers spanning the OB gene region (7q3l.3) were genotyped in 101 obese French families. Affected-sib-pair analyses for extreme obesity, defined by BMI >35 kg/m2, revealed suggestive evidence for linkage to three markers located within 2 cM of the OB gene (D7S514, D7S680, and D7S530). The OB gene is therefore a candidate for genetic predisposition to extreme obesity in a subset of these families.