Molecular diagnosis refers to the application of molecular biology methods to detect changes in the structure or expression level of genetic material in the patient's body to make a diagnosis.Molecular diagnosis is the main method of predictive diagnosis,which can be used to diagnose individual genetic diseases as well as prenatal diagnosis.Molecular diagnosis mainly refers to the detection of genes encoding various structural proteins,enzymes,antigens and antibodies,and immunologically active molecules related to diseases.

 Reasonable specimen collection is essential to ensure the integrity of specimens and the accuracy of qualitative/quantitative nucleic acid detection.Specimens should be collected strictly in accordance with appropriate biosafety guidelines.Improper specimen handling can lead to nucleic acid degradation and produce erroneous patient test results.

 1.Specimen identification

 When collecting specimens,the identity of patients and their specimens should be clarified,and patient privacy should be fully respected.At the same time,medical personnel should be provided with reasonable and sufficient information related to testing and treatment.The specimens should be firmly labeled,and the content should at least include:identification number,date and time of collection,name of specimen collector,source of specimen,etc.

 2.Application form information

 The application form includes at least the following information:identification number,admission number,patient name,date of birth,gender,race,collection date,specimen type,relevant clinical and laboratory information,doctor's name,specimen collection department,test application Reasons and so on.

 3.Specimen collection

 When collecting human tissue or body fluid samples,you should follow relevant safety precautions,wear gloves,prevent the spread of blood-borne pathogens in the specimen,and prevent the specimen from being contaminated by the exfoliated cells of the processing personnel.Specific testing methods may require additional precautions and collection instructions.For example,HPV testing should collect cervical specimens before the acetic acid test.When using different detection methods,laboratories should consider potential sources of interference and contamination,and correctly guide and train clinicians to collect specimens in accordance with specific methods or detection systems.After receiving the specimen,the clinical laboratory should enter the specimen information into the Laboratory Information System(LIS)as soon as possible,and at the same time,process the received specimen as soon as possible.If the specimen has conditions such as hemolysis,frozen blood,or improper labeling,it should be considered for rejection.

 4.Anticoagulant

 Blood and bone marrow aspiration(BMA)specimens should be collected using appropriate anticoagulation tubes or test tubes containing other additives.The choice of test tube additives should be based on the type of analyte,test,and sample volume.Studies have shown that heparin and heme may inhibit the PCR reaction.Therefore,it is recommended to use EDTA and ACD anticoagulants to detect plasma or bone marrow aspiration specimens.If it is measured as intracellular RNA,the device for collecting blood or bone marrow should contain an RNA stabilizer,or add an RNA stabilizing solution immediately after collection.

 5.Tissue specimens

 If blood or oral mucosal cells are not available(such as death of the patient),or the genotype of the tissue sample is different from that of blood or oral mucosal cells,or the tissue is the source of the nucleic acid of some potentially infectious substances,tissue samples can be used.Usually the optimal amount of tissue is 1-2g,but due to the different amounts of DNA and RNA contained in various tissues,the amount of tissue collected varies from tissue to tissue.Multicellular tissues such as bone marrow,lymph nodes,and spleen are suitable for genomic DNA testing,and require less tissue.Small-cell specimens such as muscle,fiber,and adipose tissue are not the best source of genomic DNA,and the collection amount should be greater than 1-2g.Generally,if there is no extensive fat infiltration,at least 10μg of RNA or DNA can be obtained from a tissue larger than 10 mg.The amount and type of protein in different tissues are different,and nucleic acid isolation methods vary from tissue to tissue.According to the specific source of the tissue,according to the manufacturer's recommendations to isolate DNA or RNA.

 Pathologists usually take representative tissues from large tissues for fixation,staining,microscopic examination and pathological diagnosis,or select representative tissues to extract DNA or RNA for molecular analysis.Generally,the lesion tissue is selected for detection,and the non-lesion tissue is used as a control.Control tissue is essential for certain molecular tests,such as loss of heterozygosity analysis or microsatellite instability tests.