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.

Biochemical monitoring of treatment for galactosaemia: biological variability in metabolite concentrations.

Red cell galactose 1-phosphate (Gal-1-P) concentrations and urinary galactitol excretion have been suggested as biochemical indices of dietary compliance in classical transferase-deficient galactosaemia. We report our experience of measuring both in 32 patients over 0-10.9 years (median 3.45). A total of 438 blood specimens for Gal-1-P and 383 urine specimens for galacitol assay were received; 317 pairs of specimens were collected at the same time. Concentrations of both analytes fell rapidly over the first 2-3 months following dietary intervention, to mean (geometric SD) levels of 225 (1.60) mumol/L red cells for Gal-1-P and 388 (1.19) mumol/mmol creatinine for galactitol. Concentrations then fell exponentially over the next 7-8 years, with times to half-disappearance of 6.3 years for Gal-1-P and 6.4 years for galactitol, to levels of 104 (1.58) and 193 (1.36) respectively in patients aged over 10 years. Concentrations of both analytes were independent of the presence of the common Q188R mutation. Mean intra- and inter-individual coefficients of variation (CV) across the range of values studied were 36% and 61% for Gal-1-P, and 37% and 42% for galactitol. Analytical CVs were 3.6% for Gal-1-P and 5.5% for galactitol, indicating that the major source of variability is biological. The correlation coefficient between Gal-1-P and galactitol in paired samples overall was 0.33; the regression equation being [Galactitol] = 0.84[Gal-1-P] + 176. Serial measurements of both Gal-1-P and galactitol may be valuable in monitoring galactosaemia, but high intra-individual biological variability limits their usefulness. Standardization of sample collection times may improve this. Further work is needed to assess the predictive values of both analytes for long-term outcome.

Congenital hypothyroidism, seasonality and consanguinity in the West Midlands, England.

Seasonal variation in the incidence of congenital hypothyroidism (CHT) is reported by some centres. Also, the incidence of CHT varies with ethnic origin. We report our experience in the West Midlands, England. The overall incidence of CHT among 1128 632 neonates screened over 16 years in the West Midlands was 1:2924 live births, but was increased (1:2323; p<0.05) between October and December. In the city of Birmingham between 1981 and 1991, the incidence of CHT was 1:781, 1:5540 and 1:2257 in Pakistani, Indian and North-West European children, respectively; no cases were seen in those from other ethnic groups. Consanguinity among those of Pakistani descent could account for the increased incidence within this population. Identification of the cause of seasonal variation may aid development of preventative strategies.

A comparison of disease and gene frequencies of inborn errors of metabolism among different ethnic groups in the West Midlands, UK.

OBJECTIVE: To assess birth and gene frequencies of specific autosomal recessively inborn errors of metabolism (IEM) within different ethnic groups. DESIGN: Retrospective study in a regional centre for investigation and treatment of IEM. SUBJECTS: All children born within the West Midlands NHS Region, UK, during the decade immediately preceding the 1991 National Census. METHODS: Birth frequencies for individual IEM were calculated separately for the main ethnic groups in the West Midlands using data from the West Midlands Neonatal Screening Programme, the regional register of IEM patients, and population frequencies from the National Census. Gene frequencies were calculated using previously documented observations on parental consanguinity rates and inbreeding coefficients. RESULTS: The overall incidence of recorded IEM was tenfold higher among Pakistanis compared to white children (1:318 v 1:3760), whereas only one AfroCaribbean child was identified (incidence 1:16 887). Tyrosinaemia type 1, cystinosis, mucopolysaccharidosis type 1, non-ketotic hyperglycinaemia, and hyperchylomicronaemia all occurred more frequently among Pakistanis. An increased gene frequency was only confirmed for tyrosinaemia. The incidence of phenylketonuria was similar in Pakistani and white children (1:14 452 v 1:12 611), but the gene frequency was significantly lower in Pakistanis (1:713 v 1:112). These results illustrate the interplay between gene frequency and parental consanguinity in determining disease frequencies in different populations, and indicate anticipated disease frequencies in the absence of consanguineous marriage. These figures have implications for the organisation of services for management of inborn errors, for genetic counselling, and for the assessment of gene flow in world populations.

Measurement of lactate in cerebrospinal fluid in investigation of inherited metabolic disease.

Measurement of lactate concentrations in cerebrospinal fluid (CSF) has been suggested as part of the investigation of inborn errors of the electron transport chain, but little information exists regarding the reference range in children or the relationship between CSF and plasma concentrations. In 39 children without bacterial meningitis, diabetes, or recent seizures, we determined that the median (range) lactate concentrations in CSF and plasma collected concurrently were 1.4 (0.8-2.2) and 1.5 (0.6-2.3) mmol/L; the regression equation was CSF lactate = (0.38+/-0.06) plasma lactate + 0.83 (r2 = 0.14). In 8 of 11 (73%) children with electron transport chain defects, CSF lactate was > or =3.0 mmol/L; however, 2 of these 8 had a normal plasma lactate concentration. CSF lactate was also increased in 2 children with nonketotic hyperglycinemia. The finding that CSF lactate concentrations may be increased despite a normal plasma lactate value in children with electron transport chain defects is an important clue to the diagnosis of these disorders.

Screening for tyrosinaemia type I.

AIMS: To assess the incidence of tyrosinaemia type I in the West Midlands Region, and the value of current neonatal screening programmes for phenylketonuria (PKU) for its detection. METHODS: Retrospective study of results from the PKU neonatal screening programmes in Birmingham (using plasma amino acid chromatography) and in the rest of the West Midlands (using the Guthrie microbiological assay for blood spot phenylalanine) was carried out between January 1985 and March 1994. Patients with tyrosinaemia I born in the region during the same period were identified from a regional database of patients with confirmed inherited metabolic disease. The study was carried out in a specialist children's hospital; the regional centre in the West Midlands for neonatal screening and investigation of inborn errors, and a supraregional centre for liver transplantation and management of paediatric liver disease. RESULTS: Amino acid chromatography showed increased tyrosine in 447 of 145,444 neonates born in Birmingham; this was still increased at 6 weeks of age in six cases. Five had tyrosinaemia I; the sixth had tyrosinaemia type III. Two others in whom amino acid chromatography was considered normal have since presented with tyrosinaemia I. Outside Birmingham, 525,151 children were screened using the Guthrie test. Five have presented clinically with tyrosinaemia I; screening did not contribute to diagnosis in any case. The incidence of tyrosinaemia I was 1 in 20,791 live births within Birmingham and 1 in 105,037 outside. Of the total 12 patients in the West Midlands with tyrosinaemia I, 10 (83%) were of non-oriental Asian ethnicity; the incidence of tyrosinaemia I was 3.7/10(6) head of population in this group and 0.04/10(6) in the rest of the population. CONCLUSIONS: Asians in the West Midlands have a high incidence of tyrosinaemia I. Neonatal PKU screening using amino acid chromatography may contribute to diagnosis and early treatment.

Carbohydrate deficient glycoprotein syndrome; multiple abnormalities and diagnostic delay.

A 3 week old boy presented with abnormal thyroid function, and was treated with thyroxine. He developed multisystem disease including deafness and nephrotic syndrome, and died aged 3 months. Carbohydrate deficient glycoprotein syndrome (CDGS) was diagnosed post-mortem. CDGS should be considered in all infants with apparently unrelated multiple clinical or biochemical abnormalities.

Survival in hypercalcaemic patients with cancer and co-existing primary hyperparathyroidism.

Hypercalcaemia associated with malignancy is generally thought to carry a poor prognosis. Of 47 consecutive patients with hypercalcaemia and malignancy, serum parathyroid hormone (PTH) was elevated in seven, consistent with co-existing hyperparathyroidism. Median survival from onset of hypercalcaemia in these seven patients was 817 days; compared to 33 days in the remaining 40 patients with hypercalcaemia of malignancy, in whom PTH was suppressed (p = 0.007). Among patients with hypercalcaemia of malignancy, plasma PTH-related protein (PTHrP) concentration showed no correlation with survival (r2 = 2.1%), but one patient with increased levels of both PTH and PTHrP survived only nine days after the onset of hypercalcaemia. A raised PTH had a positive predictive value of 86% for survival > 100 days, and of 71% for survival > 1 year. A raised plasma PTHrP predicted death within 100 days with a positive predictive value of 69%. We conclude that measurement of serum PTH is indicated in patients with hypercalcaemia and malignancy to identify the 15% with hyperparathyroidism, since this is associated with prolonged survival. In patients with hyperparathyroidism, assay of plasma PTHrP may indicate concurrent hypercalcaemia of malignancy, with an associated poor prognosis.

Dual bezafibrate-simvastatin therapy for combined hyperlipidaemia.

Statins and fibrates are both effective in the treatment of hyperlipidaemias but are not recommended in combination because episodes of rhabdomyolysis have followed combined lovastatin-gemfibrozil therapy. We assessed treatment with dual bezafibrate-simvastatin therapy in routine clinical practice. In 22 patients, total cholesterol, LDL-cholesterol and triglycerides fell by 20.1% (P < 0.0001), 35.1% (P < 0.001) and 31% (P < 0.05) respectively, and HDL-cholesterol rose by 18.4% (P < 0.05) on combination therapy. The reduction in cholesterol followed the introduction of simvastatin, while the decrease in triglycerides followed treatment with bezafibrate. No patient developed myopathy. We conclude that dual simvastatin-bezafibrate therapy is well tolerated and may reduce triglyceride concentrations, but offers no advantage in cholesterol reduction over treatment with simvastatin alone.

In vitro stability of endogenous parathyroid hormone-related protein in blood and plasma.

We describe a systematic comparison of the effects of anticoagulants, protease inhibitors and conditions of sample handling on the in vitro stability of endogenous parathyroid hormone-related protein (PTHrP) in blood from patients with hypercalcaemia of malignancy (HM). When blood was separated within 15 min of collection, PTHrP1-86 levels measured by two-site immunoradiometric assay in serum and heparinized plasma were significantly lower than in ethylenediaminetetraacetic acid (EDTA) plasma (P < 0.02). PTHrP was unstable in blood kept at 20 degrees C for 4 h and inclusion of protease inhibitors reduced, but failed to abolish, this instability. In blood collected in the presence of EDTA, inclusion of leupeptin either alone or in combination with pepstatin and aprotinin increased the mean half-time of disappearance from 3.9 to 10.1 and 11.2 h, respectively (P < 0.05). In contrast, when blood containing EDTA was separated within 15 min, PTHrP was stable in plasma at 20 degrees C for at least 4 h. As a result of the instability of PTHrP1-86 immunoreactivity in whole blood at ambient temperatures we advise that for our immunoradiometric assay (IRMA) blood collected in EDTA should be separated within 15 min, and the plasma frozen until assay.

Parathyroid hormone-related protein (PTHrP) gene expression in solid tumours associated with normocalcaemia and hypercalcaemia.

Parathyroid hormone-related protein (PTHrP) is an important humoral factor in the syndrome of humoral hypercalcaemia of malignancy (HHM) and its importance is evident by the many studies examining either PTHrP mRNA expression, intracellular peptide, or circulating PTHrP levels in patients with malignancy. However, the relationship between PTHrP mRNA expression, intracellular localization of peptide, and circulating PTHrP levels in the same group of patients with malignancy has not been examined. This study was carried out to explore this relationship in a group of patients with solid tumours associated with either normocalcaemia or hypercalcaemia. PTHrP mRNA and peptide were localized by in situ hybridization and immunohistochemistry respectively in 26 squamous carcinomas and 15 adenocarcinomas from patients who were either hypercalcaemic or normocalcaemic. Plasma PTHrP1-86 and serum PTH1-84 concentrations were measured by two-site immunoradiometric assays. PTHrP mRNA and peptide were localized in 11 (100 per cent) and 10 (91 per cent) of 11 squamous tumours from hypercalcaemic patients, all of whom had detectable circulating PTHrP levels, and in 14 (97 per cent) and 11 (73 per cent) respectively of 15 squamous tumours from normocalcaemic patients. PTHrP mRNA and peptide were localized in only two (28 per cent) and four (57 per cent) respectively of seven adenocarcinomas associated with hypercalcaemia. Since the majority of squamous tumours synthesized PTHrP irrespective of the calcium status of the patient, this suggests that the clinical expression of tumour-derived PTH-like bioactivity may depend on the rate of secretion of PTHrP rather than gene expression, and that the bioactivity of secreted PTHrP may be modulated by post-translational processing.

Parathyroid hormone-related protein as a tumour marker in humoral hypercalcaemia associated with occult malignancy.

The tumour-derived factor PTH-related protein (PTHRP) is the primary humoral factor responsible for hypercalcaemia in patients with solid tumours. In a woman presenting with anaemia and hypercalcaemia, the finding of raised plasma PTHRP and undetectable serum PTH concentrations led to further investigations and the subsequent identification of a uterine tumour. No evidence of tumour spread was found at operation, and removal of the tumour resulted in normalization of both serum calcium and plasma PTHRP. Expression of PTHRP by the tumour was shown by immunohistochemistry and in situ hybridization. We conclude that the identification of an occult tumour in a patient with hypercalcaemia and raised plasma PTHRP provides evidence of the diagnostic utility of PTHRP immunoassays in the investigation of patients with hypercalcaemia and suspected malignancy.

Homozygous acute intermittent porphyria: compound heterozygosity for adjacent base transitions in the same codon of the porphobilinogen deaminase gene.

A sister and brother with severe porphobilinogen (PBG) deaminase deficiency are described. Each of their parents carries a different mutation for acute intermittent porphyria and the children are homozygous for the PBG-deaminase deficiency that causes this disorder. Both are compound heterozygotes for adjacent base transitions in the same codon in exon 10 of the PBG deaminase gene.