The Mobile Shelter Laboratories (MSL) development Status study MSL is a mobile laboratory which is convenient to move and can carry out nucleic acid detection quickly and flexibly. It is composed of rigid integrated box, equipment and support system. Temperature and humidity control system, negative pressure ventilation system, power supply system, water supply and drainage system, information system and other related supporting facilities provide guarantee for the detection environment, which can meet the needs of clinical sample detection or scientific experiment activities3. The design of MSL conforms to the relevant national industry standards4. It has the characteristics of flexible design, short construction period, low cost, strong mobility and good maintainability. Mobile lab started late in China. But due to the outbreak of COVID-19 and the importance of bio-safety, the mobile lab has entered a rapid development period in China. By learning from the advanced experience of foreign mobile laboratory construction and management, the management of China's mobile laboratory began to move towards scientization, standardization and legalization5.
The Mobile Shelter Laboratories (MSL) site selection and installation requirements study The location of MSL should follow the principle of minimal impact on environment, high safety, and be close to the nucleic acid collection center, so as to shorten the transportation time. Make sure there is good ventilation and small flow of people around the shelter. Under the condition of flat site, MSL only needs to carry out box hoisting and placement, with water supply and electricity docking. In addition, around the mobile laboratory box, medical waste storage area, material storage area, staff rest area, etc. should be arranged at the same time. The layout method is as follows (fig 2.):
The internal structure of the Mobile Shelter Laboratory (MSL) We use a containerized mobile laboratory. Compared with a gas film laboratory, the biggest advantage of a containerized laboratory is that it can be used repeatedly, the built-in equipment can be integrated, no installation, and it can be vehicle-mounted, stop and go. The specific layout of the Mobile Shelter Laboratory used this time is as follows (fig3), including reagent preparation area, sample processing area, amplification analysis room and data analysis room, as well as an air-conditioning room to control the fresh air system and autoclaving chamber to ensure biological safety. The entire container is 13.716 meters long, 2.438 meters wide, and 2.896 meters high.
Operation management of the Mobile Shelter Laboratory (MSL) In order to ensure the efficient, safe and high-quality operation of the Mobile Shelter Laboratory, laboratory personnel shall be trained strictly before taking up their posts. Laboratory personnel of the MSL shall hold the post certificate of technical personnel of clinical gene amplification laboratory and the certificate of nucleic acid detection of new coronet, pass the biosafety protection training, and meet the requirements of "Administrative Measures for Clinical Gene Amplification Laboratory of Medical Institutions" 6 before they can start their work. The shifts should be flexibly adjusted according to the sample size and sample arrival time, and personnel should be scheduled reasonably. In the case of large-scale testing, a 24-hour three-shift system can be used, with one shift every 8 hours. Hardware conditions meet the "Medical Biosafety Laboratory Building Technical Standards"7, "General Criteria for Pathogenic Microorganism Laboratory Biosafety"8 and "General Requirements for Laboratory Biosafety" 9, and the negative pressure, temperature and humidity control and cleanliness level of the laboratory all meet the corresponding standards.
Quality control and management Before being used for clinical specimen testing, the laboratory shall perform necessary performance verification for the detection system consisting of extraction reagents, extractors, amplification reagents, and thermal cyclers. Performance indicators include but are not limited to precision (at least repeatability) and the lowest detection limit. It is recommended to use highly sensitive reagents (detection limit ≤ 500 copies/mL). Each batch of testing has at least 1 weak positive quality control product (third-party quality control product, usually 1.5-3 times the detection limit) and 3 negative control products (physiological saline). The negative control should be opened and placed on the extractor or operating table overnight for environmental pollution assessment. The quality control products are randomly placed in clinical specimens and participate in the whole process from extraction to amplification. However, when testing COVID-19 specimens on a large scale in the shelter laboratory, in accordance with relevant regulations, each batch of testing could randomly conduct weak positive and negative indoor quality control10. In large-scale population screening, due to the extremely low population prevalence (<0.1%), once a positive result appears, another one or two more sensitive nucleic acid detection reagents that amplify different regions are used on the original sample for the positive sample. Recheck the test, and only if the check is positive, it can be reported11. Those that do not meet the quality control requirements shall not carry out nucleic acid testin12.
Establishment and implementation of biosafety related management systems The laboratory should be equipped with biosafety guarantee equipment, including type ⅡA2 biological safety cabinet, vertical pressure steam sterilizer, circulating air disinfection machine, mobile ultraviolet disinfection lamp, accident handling box, sample transfer box, medical waste bins, etc., and equipped with adequate personal protective equipment, hand sanitizer, and hand-cleaning paper box, etc., and requires staff to strictly implement the biosafety management system, operating procedures and standard precautions, and correctly put on and take off personal protective equipment to ensure safety13. The sample transfer box needs to be wiped or sprayed with 0.2% chlorine disinfectant or 75% alcohol before and after use. After the experiment in each area, use a chlorine-containing disinfectant with an effective chlorine content of 0.2% (required to be prepared on-the-spot) to disinfect the countertops, floors and other places for at least 30 minutes. When spills occur in the laboratory, use a chlorine disinfectant with a concentration of 0.55% (5500 mg/L) to deal with it 14.