CLINICAL BIOCHEMISTRY LAQs & SAQs — Past Paper OmpathStudy

BACHELOR OF MEDICINE AND BACHELOR OF SURGERY UNIT CODE: MBMB2200 UNIT TITLE: MEDICAL BIOCHEMISTRY II (MBMB2211A: Tissue Metabolism and Integration of Metabolism MBMB2211D: Clinical Biochemistry) UNIVERSITY EXAMINATION 2021/2022 DEPARTMENT OF MEDICAL BIOCHEMISTRY DATE: TIME: 2 HOURS GOOD LUCK DAKTARI Sample Handling in Clinical Diagnosis Explain the Concept of Sample Handling in Clinical Diagnosis (5 Marks) Definition: Collection, processing, and storage of biological specimens to ensure accurate laboratory results. --- 1. Blood Sample Types & Additives (1 mark) Serum (clotted blood) → no fibrinogen Plasma (anticoagulated) → contains fibrinogen Heparin - blocks clotting factors EDTA/Citrate - bind Ca²⁺ Note: Use serum for Na⁺, K⁺, Li⁺ (anticoagulants interfere) --- 2. Special Tubes (1 mark) Fluoride tube → glucose (stops glycolysis) Urine additives: Azide/toluene → prevent bacteria HCl → Ca²⁺, Mg²⁺, phosphate(prevents precipitation). Alkaline → urate --- 3. Avoid Contamination (1 mark) No drip arm sampling Correct tube selection Proper labeling --- 4. Timely Separation (1 mark) Separate within 12 hours Delayed = false high K⁺, phosphate, LDH Hemolysis → red serum --- 5. Labile Analytes (1 mark) Blood gases → anaerobic + ice to prevent gas loss and lactic acid formation. Peptide hormones → protease inhibitors Ammonia → immediate analysis due to glutamine breakdown --- Key Points: Time-sensitive processing essential Proper handling = accurate results Wrong technique = wrong diagnosis Definition: These are the ranges of values from which the clinical parameters are measured from Significance: Aid in diagnosis – Compare patient results to normal limits. Monitor treatment – Track changes during therapy. Detect disease early – Identify abnormalities before symptoms appear. --- --- Preanalytical Phase – Key Steps (Short Notes) Preparation for Collection Patient instructions: diet, posture, urine containers . Sampling Preparation Test request , data entry, and tube labeling . Sampling Patient ID , timing, tourniquet use, site & needle positioning, tube changes. Transport Prompt collection and safe transport to lab. Sample Treatment Registration, centrifugation , mixing, and sample extraction . Storage Control of storage time, temperature , and remixing before use . --- --- Explain Ways to Detect Systematic Errors (4 Marks) Method Comparison Compare results from two different analytical methods ; significant differences suggest a systematic error. Standard Value Comparison Compare experimental result with a known standard value ; deviation indicates possible error. Use of Blank Solution Run a blank (no analyte). If it gives a reading, subtract it from the result to correct for systematic error. Inter-Laboratory Testing Analyze same sample in different labs or by different analysts ; consistent differences suggest systematic error. --- o Unlabelled sample o Mislabeled sample – any mismatch or discrepancy of identification o Insufficiently labeled sample – less than two identifiers o Transfusion labeling requirements – no collector signature, no time and date of collection o Sample suspected to be from wrong patient – wrong blood in tube Causes of Low Total Protein in Blood Liver disease – the liver makes most blood proteins. Poor diet (malnutrition) – not enough building blocks to make proteins. Too much water in blood (haemodilution) – proteins get diluted. Loss of key proteins – like albumin or antibodies (globulins). ( hypoalbuminaemia or hypogammaglobulinaemia .) Examples of Tumor Markers: Enzymes – general, not specific to one cancer type. Acid Phosphatase – seen in prostate cancer . Alkaline Phosphatase – associated with bone and liver cancers . Prostate Specific Antigen (PSA) – specific for prostate cancer . Alpha-Fetoprotein (AFP) – marker for liver cancer . Immunoglobulins – elevated in plasma cell cancers (e.g. multiple myeloma). Carbohydrate Antigen 125 (CA-125) – seen in ovarian cancer . Carbohydrate Antigen 15-3 (CA 15-3) – used in breast cancer monitoring. Isoenzyme Analysis : Separate enzyme isoforms to identify the specific tissue source. Use of Specific Inhibitors : Apply enzyme inhibitors that target particular isoenzymes, improving specificity. Glycolysis :Main energy source, anaerobic. Glucose → 2 ATP and lactate (no mitochondria). Hexose Monophosphate Shunt (Pentose Phosphate Pathway) :Produces NADPH to protect against oxidative stress. Maintains cell integrity. Lactate Production :Final product of glycolysis. Transported to liver (Cori Cycle) to produce glucose. No Mitochondria : Erythrocytes cannot perform oxidative phosphorylation, relying solely on glycolysis for ATP. Bilirubin Metabolism : Heme → Biliverdin → Bilirubin → Conjugated in liver → Excreted as bile. Unconjugated : Bound to albumin (not water-soluble). Conjugated : Water-soluble, excreted in bile. Disorders : Jaundice : Yellowing of skin/sclera. Pre-hepatic (Hemolytic) : Excess RBC breakdown. Hepatic : Liver dysfunction (e.g., hepat