Clinical biochemistry guidelines in Wales: their impact on laboratory services.

BACKGROUND: Evidence of significant variations in clinical biochemistry practice in Wales led to the formation of the All Wales Clinical Biochemistry Audit Group (AWCBAG) in 1993, with the aim of auditing laboratory services to ensure that they are optimally used. As part of this process, clinical guidelines are produced and circulated to all clinical biochemistry departments in Wales. The current aim of the AWCBAG is to assess the extent and impact of adoption of these guidelines across Wales. METHODS: Three surveys were dispatched at intervals over a decade to all clinical biochemistry departments in Wales to investigate practice in: (1) urine albumin testing to screen for diabetic nephropathy; (2) biochemical investigation of menopausal status and the monitoring of hormone replacement therapy; (3) screening for Cushing's syndrome. RESULTS: The results show that laboratories across Wales are generally following guideline criteria and are adapting their practice in-line with changing recommendations. CONCLUSION: The introduction of AWCBAG guidelines has been widely accepted by clinical biochemistry departments in Wales. These guidelines have led to a more efficient and effective use of laboratory services.

Provision of laboratory services for lipid analysis in the United Kingdom.

BACKGROUND: National guidelines have been developed in the UK to reduce coronary heart disease mortality. This audit assesses provision of lipid analyses by UK Clinical Biochemistry services to support their implementation. METHODS: Audit standards were derived from published guidelines. A questionnaire based on these was circulated to all UK Clinical Biochemistry laboratories. RESULTS: Of 108 replies, routine lipid profiles included triglycerides, HDL-, LDL-cholesterol and total:HDL cholesterol ratio in 98, 85, 72 and 44%, respectively. Only 33% and 27% analysed triglycerides and HDL, respectively, when asked simply to measure cholesterol. Seventy-six percent of the reports stated whether specimens were collected after fasting. For primary prevention, 46% of laboratories stated results should be interpreted in association with other risk factors; 20% referred explicitly to national/local guidelines. Only 19 laboratories quoted secondary prevention treatment thresholds for total cholesterol or LDL-cholesterol. Sixty laboratories occasionally added extra tests and/or interpretive comments. Eight laboratories appeared to provide no input from senior medical/scientific staff into report validation. CONCLUSIONS: These results indicate scope for improvement in the provision of lipid analyses and of information to support their interpretation. We recommend laboratories should routinely provide LDL- and non-HDL-cholesterol results, and that reports should quote treatment thresholds/targets in keeping with current guidelines.

Recommended standards for biochemical markers of myocardial damage: All Wales Clinical Biochemistry Audit Group.

The effective use of cardiac-specific troponin estimations in the diagnosis of acute myocardial infarction (AMI) is clouded by the imprecise definition surrounding the decision limits. This has led to a wide variation of criteria for the diagnosis of myocardial infarction. A survey of troponin measurements in Welsh laboratories, undertaken in 2003 under the auspices of the All Wales Clinical Biochemistry Audit Group, revealed significant variations in laboratory and clinical practice. Extensive discussion and consultation led by a working group of clinical biochemists and cardiologists in Wales culminated in recommendations concerning the use of troponin assays to establish myocardial damage. The key recommendations are: Cardiac troponin (T or I) should be the first-line test for myocardial damage; Two samples should be collected, at admission and 12-24 h later. The first sample is used for 'rule in' purposes, but not to 'rule out' myocardial damage; Only one threshold (cut-off) value for troponin should be quoted on laboratory reports, values above which are indicative of myocardial damage. A study by the Wales External Quality Assurance Scheme (WEQAS) enabled the derivation of the recommended cut-off concentrations of troponin for defining myocardial damage, defined for each assay as the concentration that can be reliably distinguished, with a confidence interval of 99%, from the 99th percentile reference limit. These recommended standards provide a rationale for a uniform approach for troponin assays for patients with chest pain, working towards a standardized approach to the diagnosis and management of patients presenting with acute coronary syndromes.

A study to determine plasma antioxidant concentrations in patients with Barrett's oesophagus.

BACKGROUND: Dietary questionnaire studies have suggested that patients with oesophageal adenocarcinoma are deficient in antioxidants. It is not known whether the same holds true for patients with the precursor lesion, Barrett's oesophagus. AIMS: To evaluate the hypothesis that patients with Barrett's oesophagus are deficient in antioxidants compared with patients without evidence of Barrett's oesophagus. PATIENTS AND METHODS: Plasma antioxidant profiles (copper, selenium, zinc; vitamins A, C, and E; carotenoids) were determined for patients with Barrett's oesophagus (n = 36), patients with erosive oesophagitis (n = 32), and patient controls (n = 35). RESULTS: Patients with Barrett's oesophagus had significantly lower plasma concentrations of selenium, vitamin C, beta cryptoxanthine, and xanthophyll compared with the other groups. CONCLUSIONS: This study confirms the hypothesis that patients with Barrett's oesophagus are deficient in certain antioxidants.

Sequential changes in plasma selenium concentration after cadaveric renal transplantation.

BACKGROUND: Previous investigations have shown that plasma selenium concentrations are significantly lower in patients with established chronic graft nephropathy (CGN) than in healthy transplant controls. The aims of this study were to determine when in the transplant process low selenium concentrations become apparent and to explore the relationship between selenium levels and risk factors for CGN. METHODS: Plasma selenium concentrations were measured in 40 patients (20 receiving cyclosporin, 20 receiving tacrolimus) undergoing transplantation. Samples were obtained immediately before transplantation and at 3, 6 and 12 months after transplantation. RESULTS: A low plasma selenium concentration was found in 30 patients at the time of transplantation but this had normalized in the majority of patients by 3 months. Plasma selenium concentrations at 3, 6 and 12 months were significantly higher than baseline values for both treatment arms, but were significantly lower at 3 months in patients who experienced either clinical acute rejection (CAR) or cytomegalovirus (CMV) infection during the preceding months. CONCLUSION: Low plasma selenium concentrations are common at the time of transplantation but appear to normalize thereafter. The identification of low selenium levels in patients who experience CAR or CMV (two important risk factors for clinically apparent CGN) suggests that the relationship between selenium and CGN warrants further investigation.

Radioimmunoassays of arginine vasopressin and atrial natriuretic peptide: application of a common protocol for plasma extraction using Sep-Pak C18 cartridges.

A rapid vacuum-driven procedure, using pre-treated Sep-Pak C18 cartridges, has been developed for the simultaneous extraction of arginine vasopressin (AVP) and atrial natriuretic peptide (ANP) from plasma. Non-specific interference was removed by fractional elution with an aqueous methanol/trifluoroacetic acid (TFA) mixture. AVP and ANP were coeluted under positive pressure with a methanol/TFA mixture and the eluates air-dried before measurement using separate radioimmunoassays. Assay ranges for AVP and ANP were 0.12-29.5 pmol/L and 0.65-162 pmol/L, respectively, with mean recoveries (standard deviation in parentheses) for AVP of 96.4% (5.5%) at a level of 11.8 pmol/L and for ANP of 94.8% (5.9%) at a level of 32.4 pmol/L. The extraction and assay procedures were validated by observing the changes in plasma AVP and ANP concentrations in normal subjects at different stages of hydration and in elderly patients during treatment for congestive cardiac failure.

Terminal complement complexes and C1/C1 inhibitor complexes in rheumatoid arthritis and other arthritic conditions.

Terminal complement complex (TCC) and C1r-C1s-C1 inhibitor complex (C1/C1 INH) concentrations were measured in plasma and synovial fluid from patients with arthritis and related to other measures of disease activity. Both TCC and C1/C1 INH concentrations were significantly increased in patients with rheumatoid arthritis (RA) compared with patients with osteoarthritis (plasma and synovial fluid, P less than 0.05) and normal subjects (plasma only, P less than 0.001). In the patients with RA, there was no correlation between plasma or synovial fluid TCC concentrations and IgM rheumatoid factor, immune complex or C1/C1 INH levels. However, in 10 patients with seronegative RA, C1/C1 INH and immune complex levels correlated significantly in synovial fluid (r = 0.69, P less than 0.05) although not in plasma (r = 0.52). Plasma and synovial fluid TCC and C1/C1 INH concentrations did not differ in rheumatoid patients with severe compared with mild joint disease (categorized by the Ritchie score). These results confirm a role for complement activation in RA but suggest that several mechanisms are involved in its pathogenesis.

Congenital adrenal hypoplasia and glycerol kinase deficiency.

An unusual case of salt-wasting in a male infant is reported. The cause was a small X-chromosomal deletion within Xp21 resulting in the syndrome of congenital adrenal hypoplasia with glycerol kinase deficiency. This syndrome can readily be diagnosed by routine biochemical tests.

Terminal complement complexes and C1/C1 inhibitor complexes in autoimmune thyroid disease.

The potential role of complement activation and the membrane attack complex in the pathogenesis of Graves' disease and Hashimoto's thyroiditis has been investigated by measuring serum concentrations of the C1r-C1s-C1 inhibitor complex (C1/C1-inh) and the terminal complement complex (TCC), and by studying the binding to thyroid tissue of monoclonal and polyclonal antibodies against TCC neoantigens. Serum C1/C1-inh and TCC concentrations were significantly increased in 29 patients with untreated Graves' disease compared with 47 healthy subjects (P less than 0.001 for both), and decreased significantly after carbimazole treatment in 18 of these patients for whom post-treatment samples were available (P less than 0.01 and P less than 0.02, respectively). The serum TCC concentration, but not that of C1/C1-inh, was also significantly increased in 15 patients with Hashimoto's thyroiditis compared with the 47 healthy subjects (P less than 0.001). TCCs were identified by immunohistochemical staining around the thyroid follicles in thyroidectomy specimens from patients with Graves' disease (six out of six) and Hashimoto's thyroiditis (two out of two); normal thyroid tissue from two subjects showed no staining. These results suggest a role for complement, in particular the membrane attack complex in the pathogenesis of autoimmune thyroid disease.

Complement component C9 in Graves' disease.

C9, the terminal component of complement, is the key part of the membrane attack complex formed as a result of complement activation; it has also been reported to be an acute phase protein. Its potential role in Graves' disease has been studied by measuring plasma C9 concentrations using an automated two-site immunoradiometric assay employing monoclonal antibodies, whose binding to thyroid tissue has also been investigated. The plasma C9 concentration in patients with hyperthyroid Graves' disease (86.3 +/- 21.6 mg/l, mean +/- SD; n = 49) was significantly increased (P less than 0.001) compared with normal subjects (60.4 +/- 13.4 mg/l; n = 48). In contrast, the plasma concentration of C-reactive protein, a marker of the acute phase response, was not significantly different between the two groups. The plasma C9 concentration in patients with hyperthyroid Graves' disease decreased significantly (P less than 0.01) after treatment with antithyroid drugs (carbimazole or methimazole; n = 14), but not after radioactive iodine (131I) treatment (n = 18). Immunohistochemical staining demonstrated that monoclonal antibody to C9 bound to the basement membranes of thyroid follicular cells of Graves' thyroid tissue but not to normal thyroid tissue. Radiolabelled monoclonal antibody to C9 bound to membrane fragments prepared from thyroid glands from two patients with Graves' disease. We conclude that C9, and by implication the membrane attack complex, may be involved in the pathogenesis of Graves' disease.

Dexamethasone suppression and energy balance: a study of anorexic patients.

The performance of the dexamethasone suppression test (DST) was investigated in 45 female anorexic out-patients (cross-sectional study) and in nine female anorexic in-patients (longitudinal study). DST non-suppression was strongly associated with negative energy balance (low body weight and low Ponderal Index) but there was no significant association with the presence of affective or neurotic disturbance in these patients. These findings cast doubt on the value of the DST in the management of depressive illness.