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Proper sample collection is crucial to ensure the integrity of samples and the accuracy of nucleic acid qualitative/quantitative experiments. Samples should be collected strictly following appropriate biosafety guidelines, as improper methods can lead to the degradation of nucleic acid and inaccurate results.

1. Sample Collection

During the whole collection, patient identity should be checked and the sample should be identified, respecting patient privacy plays a key role all the time. Adequate information related to testing and treatment should be provided to healthcare staff. Samples needed to be securely labeled with at least, identification number, collection date and time, patient's name, operator, sample source, etc.

2. Information Form

The details may include an identification number, hospital admission number, patient name, date of birth, gender, race, collection date, sample type, relevant clinical and laboratory information, physician's name, department of the collection, the reason for testing, etc.

3. Sample Collection

Collecting samples of human tissue or fluid one must adhere to safety precautions. For example, wearing gloves to prevent transmission of blood-borne pathogens and to prevent contamination from shedding cells of an operator. Specific testing may require additional caution and collection instructions; for example, cervical samples for HPV testing should be collected after acetic acid application. For using different testing methods, laboratories should consider potential sources of interference and contamination, and properly instruct and train clinical staff in sample collection requirements for specific methods or testing systems. After the sample is received, clinical laboratories should promptly record sample information into the Laboratory Information System (LIS) and process received samples promptly. Otherwise, refusal to receive samples in conditions of hemolysis, frozen blood, or improper labeling.

4. Anticoagulants

For blood or bone marrow aspiration (BMA) sample collection, appropriate anticoagulant or other additive tubes should be used. Selection of tube additives depends on analyte type, assay, and sample volume; studies show heparin and heme may inhibit PCR reactions. Therefore, EDTA and ACD anticoagulants are recommended for plasma or BMA samples. For intracellular RNA measurement, blood or bone marrow collection containers should pre-add RNA stabilizers or add RNA stabilizing solution immediately after collection.

5. Tissue Samples

Tissue samples may be used when blood or oral mucosa cells cannot be obtained (e.g., deceased patients), when tissue differs in genetic composition from blood or oral mucosa cells, or when tissue serves as a potential source of nucleic acids for certain infectious agents. Typically, optimal tissue quantity is 1-2g, although DNA and RNA content varies by tissue type. Multicellular tissues like bone marrow, lymph nodes, and spleen are suitable for genomic DNA testing with smaller tissue amounts needed. Low-cell samples such as muscle, fibrous, and fatty tissues are not ideal for genomic DNA and should ideally exceed 1-2g. Typically, tissues greater than 10mg yield at least 10μg of RNA or DNA, unless widely infiltrated with fat. Protein quantity and type vary among tissues, and nucleic acid isolation methods differ accordingly. DNA or RNA isolation should follow manufacturer recommendations based on tissue source.

Pathologists typically select representative tissue sections from large tissue samples for fixation, staining, microscopic examination, and pathological diagnosis, or select representative tissues for DNA or RNA extraction for molecular analysis. The selection of lesion tissue for testing and non-lesion tissue as controls is crucial for certain molecular tests such as heterozygous deletion analysis or microsatellite instability testing.