Molecular diagnostic platforms play a crucial role in disease diagnosis, but false positives due to sample contamination remain a core challenge affecting the accuracy of test results. Sample contamination can originate from the laboratory environment, reagents and consumables, operational procedures, or cross-contamination. Essentially, exogenous nucleic acids or contaminants interfere with the target signal, leading to misdiagnosis. To address this issue, molecular diagnostic platforms need to construct a systematic prevention and control system encompassing spatial planning, operational procedures, equipment management, and personnel training.
Rational laboratory spatial planning is fundamental to contamination prevention. Molecular diagnostic laboratories should be strictly divided into reagent preparation, sample processing, amplification, and product analysis areas. Each area should maintain physical isolation and follow a unidirectional flow principle to avoid backflow of personnel and materials that could lead to cross-contamination. For example, the sample processing area should be equipped with an independent ventilation system to prevent the spread of amplified product aerosols; when the amplification and product analysis areas are combined, negative pressure environments or aerosol removal equipment should be used to reduce the risk of contamination. Furthermore, laboratory surfaces and instrument surfaces should be regularly wiped with nucleic acid removal agents and combined with ultraviolet irradiation to destroy residual nucleic acid structures, blocking contamination transmission pathways at the environmental level. Standardizing operational procedures is crucial to reducing human contamination. Laboratory personnel must strictly adhere to aseptic techniques, such as wearing disposable gloves and masks, changing gloves promptly when handling different samples or areas to prevent hand-to-hand contamination; using pipette tips with filters to prevent liquid splashing or aerosol formation during sample aspiration; handling samples gently during aliquoting, checking tube cap seals before centrifugation to prevent spillage; and treating waste with chlorine-containing disinfectant before disposal to prevent contamination spread. For high-risk procedures, such as positive control processing, the "slow aspiration, fast dispensing" principle must be followed to reduce tip contamination risk, and sample dispensing should be completed within a biosafety cabinet to avoid aerosol splashing.
Quality control of reagents and consumables is the starting point for preventing contamination. Molecular diagnosis platforms should select consumables certified as nuclease-free/pyrogen-free, such as DEPC-treated RNA experimental consumables, and blank consumables should be randomly sampled for contamination testing during acceptance testing. Reagent preparation must adhere to the principle of single-use aliquot dispensing to avoid repeated freeze-thaw cycles that could lead to nucleic acid degradation or contamination. Use sterile containers for aliquoting, labeling them with the date and intended use, and replace them regularly. For positive controls, it is recommended to use low-concentration standards to reduce the risk of aerosol diffusion and process them in a separate area to avoid cross-contamination with other samples.
Equipment management and maintenance are crucial for ensuring experimental accuracy. Pipettes, centrifuges, PCR instruments, and other equipment must be cleaned regularly, paying particular attention to removing residues from crevices and internal parts. For example, PCR instruments can be wiped with anhydrous ethanol in the well plate holders. Pipettes should be calibrated regularly to ensure pipetting accuracy. Shared equipment such as water baths should use pure or sterile water, and containers should be replaced and sterilized weekly. Furthermore, biosafety cabinets and laminar flow hoods should have their airflow and filtration efficiency checked regularly to ensure a positive pressure sterile environment during operation and prevent aerosol intrusion.
Personnel training and a sound system are long-term mechanisms for contamination control. Molecular diagnosis platforms should regularly organize contamination control training for laboratory personnel, emphasizing aseptic operation procedures, contamination emergency response processes, and case studies. Personnel must pass the assessment before operating independently. Simultaneously, a contamination incident recording system should be established, detailing the time, experimental item, possible cause, and handling measures for false positive results, facilitating traceability and experience summarization. Through institutionalized management, the contamination prevention awareness of laboratory personnel should be enhanced, fostering a culture of "prevention first, comprehensive control."
The molecular diagnosis platform needs to construct a systematic contamination prevention and control system through multi-dimensional measures including spatial planning, operational standards, equipment management, and personnel training. Reducing contamination risks at the source, blocking transmission paths during the process, and strengthening verification mechanisms at the result end are essential to effectively address false positives caused by sample contamination and ensure the accuracy and reliability of test results.
