CLINICAL BIOCHEMISTRY LAQs & SAQs

### ****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.