Clinical biochemistry

Dr Shahida Mushtaq

What is clinical biochemistry

Clinical chemistry, chemical pathology and medical biochemistry

is the area of clinical pathology that is generally concerned with analysis of bodily fluids.

Originated in the 19th century with simple chemistry test of blood and urine

Course contents Disorders of Protein Metabolism: Non-protein nitrogenous compounds

(Urea, uric acid & amino acids): 3 lectures › Their normal plasma levels› Disease states associated with their increased and

decreased levels in the plasma. Plasma Proteins:

› Normal and abnormal levels of plasma proteins and diseases associated with increased and decreased levels.

› Immunochemistry› Components of the immune system.

Course contents (cont)Diseases associated with disorders in the immune system, multiple myeloma, systemic lupus erythromatosis, heavy-chain diseases, macroglobulinemia etc.

Clinical Enzymology› Changes in enzymatic activity in disease states

Hemoglobin› Normal and types of abnormal hemoglobins.› Pathological cases associated with abnormal

hemoglobin, e.g., thalassemia, sickle cell anemia etc.

Course contents (cont) Disorders of Lipid Metabolism

› Hyper and hypolipoproteinemia. › Atherosclerosis & lipidoses. › Fatty liver

Disorders of Electrolytes, Blood Gases &Acid-base Balance› Sodium, potassium, chloride & their diagnostic

value.› Gas transport in the blood (Oxygen & CO2).› Blood pH and its regulation.› Acidosis and alkalosis (Metabolic and respiratory) &

Pathological conditions associated with each condition.

Lab Work

Blood analysis:› Electrophoretic separation of plasma proteins.› Electrophoretic separation of plasma lipoproteins.

Estimation of serum enzymes:› LDH and its isoenzymes.› CPK and its isoenzymes.

Ornithine carbamoyl transferase.› 5-nucleotidase.› Isocitric dehydrogenase.› Sorbitol dehydrogenase.› Glucose-6-P dehydrogenase.

Aldolase› Leucine aminopeptidase.› Aspartate and Alanine Aminotransferases AST and ALT.

Lab Work

Serum electrolytes:› Chloride sodium, Potassium, Calcium,

Magnesium, Phosphorus. Urine Analysis:

› Porphyrins.› Urobilinogen, Amino Levulinic Acid

(ALA)

Recommended Books

Clinical Biochemistry, 2nd Edition, 2008, R. Luxton.

Clinical Biochemistry made ridiculously simple, 2010, Stephen Goldberg.

Clinical Biochemistry; An illustrated color text, 2008, Allan Gaw, Michael J. Murphy, Robert A.

Protein metabolic disorders(inborn errors of metabolism)

A Clinically Useful Classification

Group 1: Disorders that give rise to Intoxication

Group 2: Disorders involving energy metabolism.

Group 3: Disorders involving complex molecules.

(Proposed by JM Saudubray-2002)

Group 1: Intoxication TypeThis group includes IEM that lead to acute or progressive intoxication from accumulation of toxic compounds proximal to metabolic block.

Group 1: Intoxication Type (Cont)

Includes (Cont): Congenital Urea Cycle Defects

› Arginosuccinate Lyase Def› Ornithine Carbamyl Transferase Def

Sugar Intolerance› Galactosaemia› Hereditary Fructose Intolerance

Group 1: Intoxication Type (Cont)

Includes: Aminoacidopathies e.g:

› Phenylketoneuria (PKU)› Maple Syrup Urine Disease (MSUD)› Tyrosinaemia type I

Organic acidaemias e.g.› Methylmalonic acidaemia (MMA)› Propionic Acidaemia› Isovaleric Acidaemia

GROUP 2: DEFECTS IN ENEREGY METABOLISM

This group consists of IEM with symptoms due at least partly to a deficiency of energy production or utilization. They result from a defect in the:› Liver› Myocardium› Brain › Muscle

GROUP 2: DEFECTS IN ENEREGY METABOLISM (Cont)

Includes: Hypoglycaemic disorders

› Gluconeogenesis defects› Glycogenosis defects› Hyperinsulinism

Fatty Acid Oxidation Disorders

GROUP 2: DEFECTS IN ENEREGY METABOLISM (Cont)

Includes (Cont) Congenital Lactic Acidaemias

› Pyruvate carboxylase deficiency› Krebs Citric Cycle defects› Mitochondrial Respiratory Chain defects

GROUP 3: DISORDERS INVOLVING COMPLEX MOLECULESThis group includes diseases that involve defects in the synthesis or the catabolism of complex molecules.

These diseases are: Progressive Permanent Independent of intercurrent events Not amenable to treatment.

GROUP 3: DISORDERS INVOLVING COMPLEX MOLECULES(Cont)Includes:

Lysosomal Disorders Peroxisomal Disorders Golgi Apparatus Disorders Inborn Errors of Cholesterol

Synthesis

IEM on the basis of affected enzyme or protein

Carbohydrate metabolism› Glycogen storage diseases various› Galactosemia galactose-1-phosphate uridyle transferase,

galactose kinase› Hereditary fructose intolerance fructose bisphosphate aldolase

Amino acid metabolism› Phenylketonuria phenylalanine hydroxylase› Alkaptonuria homogentisic acid oxidase› Maple syrup urine disease branched chain ketoacid hydroxylase

Lipid metabolism › Hyper and hypo lipoproteinemia various

Steroid metabolism› Congenital adrenal hyperplasia 21-

hydroxylase

Purine metabolism› Gout various› Lesch-Nyhan syndrome HGPRT(hypoxanthine-guanine phosphoribosyl transferase)

Lysosomal storage disease› Tay-sachs disease…….. hexosaminidase A› Gaucher’s disease…….. glycosylceramidase

Cell transport defects› Cystinuria………. amino acid transport› Renal glycosuria………. glucose transport› Renal tubular acidosis…. hydrogen ion

transport

Some facts

About 5 million children die in the first month of life in developing countries

Four million children are born with some congenital anomaly.

WHO

The baby –Some facts (cont)

Almost 27 - 30 % of babies dying of SIDS are now proved to be having some Inborn Errors of Metabolism (IEM).

About 5 to 15 % of all sick neonates in NICU are expected to have some IEM

WHO

IEM a single gene defect causes a clinically significant block in a

metabolic pathway resulting either in accumulation of substrate behind the

block or deficiency of the product

IEM arises from a damaged gene which leads to abnormal enzyme.

May be autosomal or sex-linked. May be recessive or dominant in

expression. Heterozygote will have both normal

and abnormal alleles. But homozygote will have two alleles the same on each chromosome.

Investigations An accumulation of the substrate before the enzyme

defect*. A decrease in the amount of the product is observed. An increased concentration of the alternative

metabolites*. A decrease or absence of the enzyme activity.

Investigations

Screening for IEM who do not have the symptoms

Investigations of the patient with symptoms of the IEM

Screening of newborn

Laboratory Diagnosis of IEM

May be carried out in three stages:a. Diagnosis of Broad Category: Saudubray

et al (2002)* suggested a battery of simple and routine tests for identification of the broad category of the disorders. These tests include plasma electrolytes, ABGs, blood ammonia and lactic acid etc.

*Saudubray JM, Nasoogne MC, Lonlay PD, Touati G. Clinical approach to inherited

metabolic disorders in neonates: an overview. Smin Neonatol 2002; 7: 3-15.

Laboratory Diagnosis of IEM (cont)

May be carried out in three stages:b. Diagnosis of the exact disorder• It requires very sophisticated

equipment e.g. HPLC, tandem mass spectrometry, GC-MS and ion exchange chromatography.

Laboratory Diagnosis of IEM (Cont) May be carried out in three stages:

b. Diagnosis of the exact disorder (cont)• These techniques also require

elaborate infrastructure of trained manpower, proper back-up service for the instruments and regular supply of reagents.

Laboratory Diagnosis of IEM

May be carried out in three stages:b. Diagnosis of the exact disorder (cont)• AKU hospital has taken an initiative to

establish the first-ever lab in the country for the pin-point diagnosis of some of the IEM.

Laboratory Diagnosis of IEM (Cont)May be carried out in three stages:

c. Determination of deficient enzyme or protein Although a few laboratories in the world provide this facility, this is only of academic and research interest. Diagnosis of the genetic defect provides another promising pathway for some of these disorders.