Laboratory Techniques 4 PDF

Samples collection and handling Sample collection and handling are critical steps in any laboratory process, as they directly influence the accuracy, reliability, and quality of test results. Whether in clinical diagnostics, research, or environmental testing, improper sample collection or mishandli...

Samples collection and handling Sample collection and handling are critical steps in any laboratory process, as they directly influence the accuracy, reliability, and quality of test results. Whether in clinical diagnostics, research, or environmental testing, improper sample collection or mishandling can lead to inaccurate results, costly errors, and even safety risks. Sample collection refers to obtaining a specimen from a person, animal, environment, or substance for analysis. Types of Laboratory Samples  Clinical Samples: o Blood (venous, arterial, capillary), Urine, Sputum, Tissue Biopsies, Saliva, Feces  Environmental Samples: o Air, Water, Soil, Food, Surfaces (for contamination or quality testing)  Microbiological Samples: o Swabs, Cultures, Stool, Sputum, Blood Cultures Sample Collection Techniques  Blood Collection: o Venous: From veins using needles or vacutainer tubes (e.g., antecubital fossa). o Capillary: From fingers or heel sticks, used for glucose tests or pediatric blood tests. o Arterial: From arteries for blood gas analysis (e.g., radial artery). 1   Urine Collection: o Midstream: Avoids contamination from urethra (commonly used for urinalysis). o 24-Hour Urine Collection: Used to measure kidney function, protein excretion, etc. o Catheterized Urine: For patients unable to provide samples independently.  Sputum Collection: o Induced Sputum: Used for microbiological testing of respiratory infections like tuberculosis. o Natural Coughing: Involves deep coughing to bring up material from the lower respiratory tract.  Tissue Biopsy: o Collected via needle biopsy or surgical excision for histopathological testing. o Needle Aspiration: For smaller tissue samples; typically used for tumors, lymph nodes, etc. Proper Labeling and Documentation  Labeling Requirements: o Patient Information: Name, age, sex, medical record number, etc. o Sample Details: Type, collection date/time, test required. o Collection Method: E.g., "midstream urine," "fasting blood sample."  Documentation: o Tracking Sheets: Ensure traceability of each sample and prevent mix-ups. Preventing Contamination  Aseptic Techniques: o Always use sterile containers and equipment to avoid introducing foreign organisms. o Personal Protective Equipment (PPE): Gloves, lab coats, face shields as necessary. o Sterile Swabs: For microbiological samples to prevent contamination. 2  o Avoiding Cross-Contamination: Separate tools for each sample, clean surfaces frequently. Temperature Control and Sample Preservation  Temperature Control: o Refrigeration: Some samples, like blood or urine, need to be kept at 4°C to slow down microbial growth and enzymatic activity. o Freezing: For plasma/serum samples to preserve their components for long-term storage. o Room Temperature: Certain samples (e.g., coagulation tests) need to be processed immediately at room temperature. Laboratory specimen storage temperature requirements : Storage Method Centigrade (Celsius) Temperature Range Refrigerated 2–8ºC Frozen less than or equal to -20 º C Room/ Ambient 20 – 25 º C  Preservation: o Biological Samples: Use preservatives (e.g., formalin for tissue) to preserve integrity. o Chemical Preservation: Stabilizers like formaldehyde for environmental or chemical samples. Sample Transport and Handling  Packaging: o Secure Containers: Biohazard bags for infectious samples, leak-proof containers for fluids. o Temperature Control: Insulated coolers, ice packs, or thermostatic containers for temperature-sensitive samples. 3   Special Handling: o Infectious Samples: Use biohazard symbols and proper packaging for transport. o Radioactive Materials: Specialized containers with shielding. Sample Preparation  Blood Samples: o Centrifugation: To separate serum or plasma from blood cells. o Aliquoting: Splitting samples into smaller portions for different tests.  Microbiological Samples: o Cultures: Inoculate media to grow bacteria/viruses. o Smears and Stains: Prepare slides for microscopic examination (e.g., Gram staining).  Tissue Samples: o Fixation: Preserve tissue with formalin or other fixatives. o Embedding and Sectioning: Embedding in paraffin and cutting thin sections for histopathology. Common Challenges in Sample Handling  Contamination: Proper sterilization and PPE are critical to avoid contamination.  Degradation: Improper storage or transport can degrade sensitive samples like blood or DNA.  Volume Limitation: Small sample sizes may require multiple aliquots or pooling to ensure sufficient material for testing. 4   Time Constraints: Some tests need to be processed immediately, which requires rapid sample transport. Best Practices for Sample Collection, Handling, and Transport  Before Collection: Always prepare with the proper containers, labeling, and necessary PPE.  During Collection: Use aseptic techniques, label immediately, and document collection details.  After Collection: Handle with care, ensure correct storage and transport conditions.  During Transport: Prioritize temperature control, timely 5