Key Points for Contamination Prevention Strategies and Quality System Development in Pathogen Nucleic Acid Testing Laboratories

Sources and Hazards of Contamination in Nucleic Acid Testing Laboratories

The most common risks in pathogen nucleic acid testing laboratories are aerosol contamination from amplification products and cross-contamination between samples. Amplification products are present at high concentrations; once they form aerosols and settle on work surfaces, pipettes, or reagent bottles, subsequent experiments are prone to weak false positives. Cross-contamination between samples is usually caused by improper handling, reuse of consumables, or carryover from automated pipetting systems. Contamination events not only affect the results of a single batch but may also lead to re-testing of an entire batch, delayed reporting, and even damage to the laboratory's reputation.

Laboratory Zoning and Airflow Organization

Proper zoning is the foundation for reducing contamination. Generally, a reagent preparation area, sample preparation area, amplification area, and product analysis area are established, connected by buffer rooms, with unidirectional flow of personnel, materials, and airflow. The reagent preparation area should maintain positive pressure, the sample preparation area may maintain negative pressure, and the amplification area and product analysis area also require control of aerosol escape. Each area should use dedicated work clothing, shoe covers, and laboratory consumables, and reverse transfer is strictly prohibited. Environmental samples from each area should be tested regularly to assess whether residual target nucleic acid is present.

Contamination Prevention Measures at Key Operational Steps

Pipetting operations should be performed in a biosafety cabinet or clean bench to avoid rapid, repeated pipetting that generates aerosols. Pipette tips should be filter tips and replaced promptly after pipetting. Reagents should be aliquoted following the principle of small volumes and multiple portions to avoid repeated freeze-thaw cycles and prolonged exposure with caps open. Amplification tubes should be briefly centrifuged before amplification to ensure no droplets remain on the tube walls. After amplification is completed, product tubes should be opened in the product analysis area and must never be opened in the sample preparation area. Work surfaces should be wiped daily with nucleic acid removal agents or effective chlorine solutions, and equipment such as pipettes and centrifuges should be cleaned regularly.

Performance Verification and Quality Control System

Before new reagents or new test items are put into use, analytical performance verification should be completed, including precision, analytical sensitivity, specificity, interference resistance, and suitability for different sample types. In routine operation, negative controls, positive controls, and internal standards should be included for monitoring. Quality control materials may use commercial reference materials or validated clinical sample dilution panels. When quality control data show trend shifts or are out of control, sample testing should be stopped immediately, the causes analyzed, and corrective measures taken. Laboratories should establish a retained-sample re-testing system to review suspicious results using the original sample or a newly collected sample.

Personnel Training and Record Management

Pathogen nucleic acid testing operations are meticulous, and personnel training should cover modules such as biosafety, sample receipt, nucleic acid extraction, amplification operations, result interpretation, and instrument maintenance. New personnel should be assessed and found qualified before taking up their posts, and experienced staff should regularly participate in competency assessments and blinded sample evaluations. Laboratory operation records include reagent lot numbers, instrument status, ambient temperature and humidity, quality control data, and handling of abnormal events. Complete records are the basis for problem tracing and quality improvement and also facilitate response to supervisory inspections or interlaboratory comparisons.

Common Misconceptions and Continuous Improvement

Some laboratories rely excessively on the sensitivity specifications of commercial kits while neglecting pre-processing steps and operational standards, resulting in actual testing performance lower than expected. Some laboratories focus only on positive results and lack unified interpretation rules for weak positives and atypical curves. Building a quality system is not a one-time task; it should be continuously optimized in conjunction with internal audits, management reviews, and external quality assessment results. Only by regularly analyzing false-positive, false-negative, and invalid run events and improving zoning layout, operating procedures, and personnel training content can the accuracy and stable output capability of pathogen nucleic acid testing reports truly be enhanced.