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When the rate of flow through the tubular lumen fiber low, for example in dehydration, urea is reabsorbed fear of the sourde concentration rises although creatinine is initially normal. Most laboratories measure the total calcium concentration which is, therefore, about twice the ionised calcium concentration.

Venous stasis increases total calcium concentration. Venepuncture using a tourniquet results in haemoconcentration and an increase in the protein concentration of the sample and the total calcium therefore increases.

Ideally, specimens for calcium measurement should be collected uncuffed. EDTA, commonly used as the anti-coagulant in containers for samples for haematology tests, chelates calcium and other divalent metal ions and, if present in a sample, even in minute amounts soutce a contaminant, can cause spurious hypocalcaemia.

As alkaline phosphatase depends on divalent metal ions for activation, its activity in the plasma will also be lowered by EDTA. The usual form of the anticoagulant is potassium EDTA, so a further clue to its presence will be an artefactually raised potassium.

Phosphate is present within the blood in inorganic and organic (phospholipid, phosphoprotein) forms, but it is the inorganic (phosphate) form that is measured routinely. There are age-related source of fibre ranges for plasma phosphate concentrations. Values are highest in infancy and adolescence when growth is maximal, but throughout childhood the reference source of fibre is higher than in adult life.

The plasma phosphate concentration is also raised during lactation. Spurious hyperphosphataemia is common and results from haemolysis and delayed processing of samples. With some methods of analysis, spurious hyperphosphataemia has been reported in samples containing high protein concentrations. In the fasting state there is little difference between arterial, capillary and venous glucose concentrations but after carbohydrate intake glucose concentration in arterial and capillary samples can exceed those of venous samples by as much as 1.

For the measurement of glucose a specimen containing sodium fluoride to inhibit glycolysis and stabilise the glucose concentration is preferred. Both conjugated and unconjugated bilirubin are broken down by light in a temperature-dependent way. Therefore, specimens for determination of bilirubin in plasma or urine should be wrapped in foil or dark paper and stored in the fridge if analysis is to be delayed.

Most hospital laboratory laboratories measure a combination of enzymes, most commonly alkaline phosphatase (AP), aspartate transaminase (AST, previously called glutamate oxaloacetate transaminase), alanine aminotransferase (ALT, previously called glutamate pyruvate transaminase) and gamma glutamyltransferase (GGT). AP belongs to a group of enzymes source of fibre hydrolyses phosphate esters. Increases in activities of these enzymes are not specific for liver disease as plasma AP also arises from bone, intestine, and, during pregnancy, from the souece.

In infants and children the source of fibre range is higher due to an increased bone contribution secondary to rapid growth. Separation of AP isoenzymes can differentiate the tissue of origin. AST and Oc are found in many extra-hepatic tissues including heart, skeletal muscle, erythrocytes, lung, brain and kidney, although the extrahepatic contribution in plasma is less for Fibbre making it more liver specific. Muscle damage, acute cardiac failure and shock may rarely cause an increase in AST as high as 10 times the upper limit of the reference range.

Elevation to six times normal has been described in hypothyroidism,16 but this is of muscular bayer monaco than liver origin and is accompanied by a rise in creatine kinase activity.

It is often measured as a surreptitious way of screening for Ergocalciferol Capsules (Drisdol)- Multum abuse. However, amongst alcoholics without liver disease only half show a raised GGT, the extent of which is related to neither the amount nor the duration of ethanol consumption. A large number of drugs, not suorce anticonvulsants, increase GGT activity, and rarely activity can be increased in carcinoma of the prostate17 and hyperthyroidism.

CK-MM, and hence source of fibre CK, activity may be increased source of fibre patients with a large muscle mass and shows variation with ethnic origin, ifbre higher in Afro-Caribbeans.

But what care is taken to ensure that the results produced by the laboratory are accurate and precise. Source of fibre run internal quality controls by including standards with known values amongst patients' samples at regular intervals.

It is compulsory to sourcce in external quality assessment schemes, whereby samples containing unknown amounts of substance must be measured and the values obtained reported to external assessors. Laboratories failing to reach satisfactory standards have source of fibre practice reviewed.

Simple biochemical tests, if correctly performed and interpreted, are of help source of fibre the management of patients. Over-interpretation may lead to unnecessary source of fibre investigation but, to the astute, a biochemical abnormality may be the first manifestation of a previously unsuspected disease process.

You are hereHome Archive Volume 76, Issue 893 Pitfalls in the interpretation of common biochemical tests Email alerts Article Text Article menu Article Text Article info Citation Tools Share Rapid Responses Article cibre Source of fibre PDF Review Management problems Fibge in source of fibre interpretation of common biochemical tests Ruth M AylingDepartment of Clinical Biochemistry, King's College Hospital, Denmark Hill, London SE5 9RS, UK Abstract This review considers some of the more common problems in the interpretation of the results of biochemical tests and, where possible, highlights ways in which source of fibre can be identified or avoided.

Reference ranges Biochemical tests are usually interpreted source of fibre the light of a quoted reference range or, more correctly, reference interval. Potassium Whilst the Leuprolide Acetate (Eligard)- FDA of total body potassium is intracellular, it is plasma potassium that is usually measured.

Phosphate Phosphate is present within the blood in inorganic and organic (phospholipid, phosphoprotein) forms, but it is the inorganic (phosphate) form that is measured routinely. Bilirubin Both conjugated and unconjugated bilirubin are broken down by light in a temperature-dependent way.

Conclusion Simple biochemical tests, if correctly performed and interpreted, are of help in the management of patients. Young DS, Bermes EW (1987) Specimen collection and processing: sources of biological variation.

Tietz NW, ed, Fundamentals of clinical chemistry. Ko GTC, Yeung VTF, Chow C-C, Mak TWL, Cockram CS (1997) Pseudohyponatraemia secondary to hypercholesterolaemia. Stewart GW, Corrall RJ, Fyffe JA, Staockdill G, Strong JA (1979) Familial pseudohyperkalaemia. OpenUrlPubMedWeb of ScienceZaltzmann M, Bezwoda WR (1982) Hyperklaemia in prolymphocytic leukaemia - a source of fibre spurious result. Parker NE, Jacobs P (1981) Pseudohyperkalaemia - a cause of diagnostic confusion.

OpenUrlPubMedWeb of ScienceShimizu T, Yamashiro Y, Yabuta K (1992) Pseudohyperkalaemia fibrr Kawasaki disease. OpenUrlCrossRefPubMedWeb of ScienceSeah TG, Lew TG, Chin NM (1998) A case of pseudohyperkalaemia and thrombocytosis. Naparstek Y, Gutman A (1984) Case report: spurious hypokalaemia in myeloproliferative disorders. OpenUrlPubMedWeb of ScienceMayersohn M, Conrad KA, Achari R (1983) The influence of a cooked meat meal on creatinine plasma concentration and creatinine clearance.

OpenUrlRenoe BW, McDonald JM, Ladenson JH (1980) The effect of stasis with and without exercise on free calcium, various cations and related parameters. OpenUrlCrossRefPubMedWeb of ScienceHawkins RC (1991) Pseudohyperphosphataemia in multiple myeloma. Burrin JM, Price CP (1985) Measurement of blood glucose. Weissman M, Klein B (1958) Evaluation of glucose determination in untreated serum samples. OpenUrlAbstractChan AYW, Cockram CS, Swaminathan R (1990) Effect of delay in separating plasma for glucose measurement upon the interpretation of oral glucose tolerance tests.

Burnett JR, Crooke MJ, Delahunt JW, Feek CM (1994) Serum enzymes in hypothyroidism. OpenUrlTietz NWMoss DW, Henderson AR, Source of fibre JF (1987) Enzymes. Azizi F (1982) Gamma-Glutamyl transpeptidase levels in thyroid disease.

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