Dr Mohamed Mahmoud Nour Eldein Ph D Biochemistry

Dr/ Mohamed Mahmoud Nour Eldein Ph. D Biochemistry Assistant Professor of Biochemistry Faculty of Medicine Umm AL-Qura University

• Biochemical investigations are involved in many branches of clinical medicine • Physicians use laboratory tests to 1 - Diagnose a disease 2 - Monitor its progress 3 - Response to treatment 4 - Screen for diseases in apparently healthy individuals • Many Factors either biological and physical (pre-analytical) or analytical may affect test results

SPECIMEN The different biochemical investigations can be performed upon different types of specimens to diagnose or to follow the defect causing the disease. These different specimens are • Tissues: include receptors, cell membrane, cytosol and nucleus • Body fluids: Blood (serum and plasma), Cerebrospinal fluid (CSF), Pleura fluid, ascites, joint (Synovila) fluid, amniotic fluid. • Secreations: Sputum, saliva, and urine

Techniques in biochemical analysis • Spectrophotometric assays observe change in the absorbance of light between products and reactants; Spectrophotometric assays are most convenient since they allow the rate of the reaction to be measured continuously. If this light is in the visible region you can actually see a change in the color of the assay, these are called Colorimetric assays. • Enzyme assays are laboratory procedures that measure the rate of enzyme reactions. Because enzymes are not consumed by the reactions they catalyze, enzyme assays usually follow changes in the concentration of either substrates or products to measure the rate of reaction • Radiometric assays • Fluorometric assays • chemiluminescence assays • Chromatographic assays

Specimen Collection • Requisition form must be completed with care Ø Patient identification Ø ID Ø Age Ø Sex Ø Physical disposition • Labeling of the sample ( in the appropriate container) matched with that on the requisition form • A variety of specimens are used in biochemical analysis. However , the majority of biochemical tests are performed on venous blood or urine

Blood specimens • Whole blood sample: Indicated in some tests (Hematology, blood gases, Hb. A 1 c…). Blood is drawn into a tube containing an anticoagulant. • Serum: is the recommended blood specimen for many biochemical analyses. Blood is withdrawn into a plain tube and allowed to clot, after centrifugation a serum specimen is obtained. • Plasma: Identical to serum in addition to coagulation factors, is recommended in some tests (where the analyte is unstable or in coagulation tests). The blood is withdrawn into a tube containing an anticoagulant, centrifuged, the supernatant is called plasma. Note: serum and plasma samples can be stored in 4Ċ for short storage periods and in -20 Ċ for long periods.

Urine Specimens • Urine containers may be plain or include a preservative to inhibit bacterial growth, or acid to stabilize certain metabolites. • Timing for collection and volume collected are essential in urine analysis and must be considered. Another Specimen types Specific body fluids or tissue may be required for some analysis. There will be specific protocols for the handling. These specimens include: • Whole blood (Venous and arterial), serum or plasma blood. • Urine • Feces • Semen • Cerebrospinal fluid (CSF), pleural fluid, ascites, joint (Synovial) fluid, amniotic fluid • Sputum and saliva

Analyzing the specimen • The analytical process includes the following items: 1 - Patient Identification. 2 -Equipment reliability(Instrument and pipette calibration). 3 - Adequate calibration • calibration curve: is a general method for determining the concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples of known concentration • control sample: is a sample (same fluid of the unknown to be analyzed) but with known concentration of the analyte to be estimated. 4 - Procedure reliability using standard operating manuals. 5 -The educational background and training of the laboratory staff.

Biochemical results and calculation • Most biochemical analyses are quantitative • Once the results are available they are collected and report is issued, providing an aid to the monitoring of treatment. • Many tests measure the amount of the analyte in a small volume of the sample, blood, plasma, serum, urine or some other body fluid. In order to be able to express concentration MASS UNIT VOLUME UNITS 1 gram (g) 10 -3 Kg 1 Liter (L) 1000 ml 1 milligram (mg) 10 -3 g 1 deciliter (dl) 10 -1 L = 100 ml 1 microgram (µg) 10 -6 g 1 milliliter (ml) 10 -3 L 1 nanogram (ng) 10 -9 g 1 microliter (µl) 10 -6 L 1 picogram (Pg) 10 -12 g Note 1: Enzymes are usually expressed as enzyme activity ‘Units’. Note 2 : The different analytes in biochemistry differ in its quantity in body, hence the technique and the expressed units are differed.