Alan E. Clague

Neonatal biochemical screening for disease

BACKGROUND The practice of screening the neonatal population for certain diseases by biochemical testing of a dried blood spot is an established public health initiative in many countries. The diseases for which screening is done vary from region to region, based on ethnic, financial and political considerations. Criteria have been established to identify diseases suitable for neonatal screening. DISEASES SCREENED In Western countries, screening for phenylketonuria (PKU) and congenital hypothyroidism (CH) has been introduced throughout. Subsequently, cost-benefit analysis has confirmed the existence of a financial benefit. Other diseases screened for in some regions include galactosemia, aminoacidemias and organic acidemias, cystic fibrosis, congenital adrenal hyperplasia, biotinidase deficiency, hemoglobinopathies, glucose-6-phosphate dehydrogenase deficiency, and Duchenne muscular dystrophy, although in no case has a clear financial benefit been established. CONCLUSIONS Since the introduction of neonatal screening over 40 years ago, new methods have resulted in an increase in the number of diseases amenable to screening, better automation and greater specificity. Methods currently used include growth of an inhibited bacterial auxotroph (the original phenylalanine (phe) method of Dr. Robert Guthrie), spectrophotometry, fluorometry, immunoassay, and tandem mass spectrometry with electrospray ionization.

Routine use of hair root or buccal swab specimens for PCR analysis: Advantages over using blood

We report the use of hair roots and buccal cells as specimens of choice for DNA analysis of genetic diseases in a service laboratory. Our protocols using these specimen types show superiority to those using blood specimens in the areas of collection, transport, storage and overall cost. Our experience using these specimen types for 319 cystic fibrosis delta F508 mutation tests and 62 Lebers hereditary optic neuroretinopathy mutation tests leads us to recommend that hair roots and buccal cells should be evaluated as specimens of first choice when developing PCR DNA analysis.

Clinical utility of serum soluble transferrin receptor levels and comparison with bone marrow iron stores as an index for iron‐deficient erythropoiesis in a heterogeneous group of patients

Aim: To evaluate the correlation between raised soluble transferrin receptor (sTfR) and stainable marrow iron, and to define the utility of sTfR in discriminating between the presence or absence of iron‐deficient erythropoiesis in patients with anaemia of chronic disease. Methods: Seventy‐six consecutive adult patients without accelerated erythropoiesis who had undergone bone marrow (BM) aspiration/trephine for various clinical reasons during 2003–2006 were studied. All patients had serum iron studies (iron, transferrin and ferritin) and sTfR performed within 1 week of BM aspiration/trephine. These 76 patients were assigned to three groups based on the iron status of the BM and sTfR level: patients with normal sTfR and normal BM iron stores (n = 49), patients with an elevated sTfR and normal BM iron stores (n = 13) and patients reduced or absent BM iron stores (n = 14). Means (95% confidence interval) for mean corpuscular volume (MCV), mean corpuscular haemoglobin concentration (MCHC), red blood cell haemoglobin (RBC Hb) content and median (5th and 95th percentiles) for haemoglobin were then calculated. Results: All patients with absent BM iron stores had an elevated sTfR level. Patients with normal BM iron stores and elevated sTfR levels had significantly lower Hb, MCV, MCHC and RBC Hb content than patients with normal BM iron stores and normal sTfR levels. Conclusion: sTfR is the most sensitive serum biochemical marker for the identification of iron‐deficient erythropoiesis. Normal BM iron stores can coexist with elevated sTfR and decreased MCV and MCHC. sTfR levels correlate better than BM iron stores with decreased MCV and MCHC. Therefore, sTfR is a useful marker of iron‐deficient erythropoiesis, due to both absent iron stores, and restricted iron supply due to anaemia of chronic disease. As a single investigation, however, sTfR does not discriminate between these two causes of iron‐deficient erythropoiesis.

Relationships between blood levels of fat soluble vitamins and disease etiology and severity in adults awaiting liver transplantation.

Background and Aims:  Although malnutrition is common in liver disease, there are limited data on fat soluble vitamins in various diseases. The aims of this study were to: (i) determine fat soluble vitamin levels in patients assessed for liver transplantation; (ii) compare levels between different disease etiologies (hepatocellular and cholestatic) and between subgroups of hepatocellular disease; and (iii) assess the multivariate contribution to vitamin levels of etiology and various indicators of disease severity.

Dark adaptation in vitamin A-deficient adults awaiting liver transplantation: improvement with intramuscular vitamin A treatment.

Background/aims Although vitamin A deficiency is common in chronic liver disease, limited data exist on impairment of dark adaptation and response to therapy. The aims were (1) to assess dark adaptation in patients, (2) to assess the relationship between dark adaptation and vitamin A status, zinc and Child–Pugh score, (3) to compare perceived and measured dark adaptation and (4) to assess the dark adaptation response to intramuscular vitamin A. Methods This was a prospective study of 20 patients (alcoholic liver disease 10, other parenchymal diseases six, cholestatic diseases four) awaiting liver transplantation. Selection was based on low serum retinol. There were 15 age-matched controls. Dark adaptation was measured with a SST-1 dark adaptometer and perception by questionnaire. Eight patients received 50 000 IU of retinyl palmitate, and dark adaptation was repeated at 1 month. Results Forty per cent of patients had impaired dark adaptation. Patients with alcoholic liver disease were more impaired than those with other parenchymal diseases (p=0.015). No relationship was found between dark adaptation and the biochemical indicators or Child–Pugh score. Seventy-five per cent of patients with impairment did not perceive a problem. After intervention, light of half the previous intensity could be seen (p=0.05). Conclusions Dark-adaptation impairment was common, was worse in alcoholic liver disease, was largely not appreciated by the patients and improved with vitamin A treatment.

Carnitine in dried blood spots: a method suitable for neonatal screening.

A method is described which enables the quantitative determination of both free and total carnitine levels in dried blood spots. This method is suitable for neonatal screening for either primary or secondary carnitine deficiency. The 95% confidence interval for free carnitine was 26-76 mumol/l (median = 44) and for total carnitine was 35-102 mumol/l (median = 60).

Chronic copper toxicosis presenting as liver failure in an australian child

&NA; A 20 month old Caucasian male child, after a five week illness, developed liver failure which was successfully treated by liver transplantation. The explanted liver had a histology identical to that seen in Indian childhood cirrhosis and its copper content was increased tenfold. Water used to prepare the childs milk feeds came from a bore via copper conduits and at times contained 120 µmol/l of copper, eight times the recommended maximum for human consumption. Because non‐Indian cases of Indian childhood cirrhosis associated with excess copper ingestion are increasingly being recognised, and as early treatment can restore normal liver morphology, we support the use of the previously suggested alternative term for this condition, ie; ‘copper‐associated liver disease in childhood’. Measurement of hepatic copper concentrations in all children less than six years of age who develop hepatic failure of unknown cause will increase its recognition. On diagnosis sources of increased dietary copper should be investigated to ensure that younger siblings are not similarly exposed.

Paraquat and diquat interference in the analysis of creatinine by the Jaffé reaction

&NA; Paraquat and diquat were shown to interfere significantly in the measurement of plasma creatinine by the alkaline picrate (Jaffé) reaction in a young man who ingested a massive dose of a mixture of the 2 herbicides. It is likely that these bipyridylium compounds react in a manner similar but at different rates compared with creatinine in the Jaffé reaction.

Broadsheet number 40: The diagnosis of renal tubular acidosis

INTRODUCTION Renal tubular acidosis (RTA) refers to a condition in which there is metabolic acidosis due to impairment of renal tubular function, often unaccompanied by decreased glomerular filtration rate. It may occur as an isolated defect or as part of a clinical syndrome involving other disorders of renal function (eg; Fanconi syndrome) or extrarenal disease (eg; Sj6gren syndrome). RTA is usually first suspected by the discovery of metabolic acidosis (low plasma HCO3) accompanied by an absolute or relative hyperchloremia and a normal anion gap, 1 (ie; Na ÷ C1 HCO3 < 15). However, since hyperchtoremic acidosis may occur for other reasons, the definitive establishment of the existence of RTA in such a patient may be desirable.

In thiamine deficiency, activation of erythrocyte transketolase by thiamine in vivo exceeds activation by cofactor in vitro

In 60 thiamine deficient patients, the mean erythrocyte transketolase activity after activation by thiamine diphosphate cofactor in vitro, representing the apparent sum of holoenzyme and apoenzyme activities, was 0.609 (SD 0.166) U/g Hb before thiamine therapy and rose to 0.772 (SD 0.152) U/g Hb immediately after the administration of thiamine to the patients. The difference between these values, 0.163 (SD 0.130) U/g, is the mean activity of transketolase protein which can be activated by thiamine in vivo but not by thiamine diphosphate in vitro. This difference correlated with low initial erythrocyte transketolase activity in these patients, but not with their alcohol intake, liver function or diagnoses.