Integrated mobile container PCR laboratory (IMCPL): A novel strategy to reduce unnecessary rapid antigen testing.

Kretschmer et al. reported in this journal that SARS-CoV-2 lateral flow tests (LFT) for rapid antigen testing resulted in an unnecessary burden in Germany with statistics on rapid antigen testing conducted in Cologne, in May 2021. In this study, they used the PCR test to determine the false positive rate of the antigen test. The results showed that the total false positive rate of rapid antigen detection was as high as 46.28%. Andreas and colleagues concluded that “From a pure laboratory and diagnostic point of view it has to be concluded that the usage of an antigen testing strategy with a false detecting rate of about 50% is unacceptable.”

To obtain the insights into the economic burden of rapid antigen testing, they calculated the direct costs arising from the performed tests and the indirect costs arising from the subsequent quarantine. The authors further concluded that “the use of rapid antigen testing only appears appropriate in high prevalence/incidence situations, because a (too) low prevalence may increase the risk of false-positive results leading to unnecessary quarantine and high economic burden.”

Currently, the diagnosis of COVID-19 is mainly based on testing SARS-CoV-2 RNA load using quantitative real-time polymerase chain reaction (qRT-PCR). Although the detection method using qRT-PCR has been considered as the benchmark among the currently available diagnostic approaches, strategies to rapidly scale up the testing for SARS-CoV-2 must be considered for future diagnostic testing, particularly dealing with the circumstances encountered worldwide in the past year. Nucleic acid testing usually requires considerable laboratory equipment and staff, and test results may take several days to become available to the physician. Therefore, rapid antigen testing is a crucial supplement to nucleic acid testing for COVID-19 management with the test results obtained rather quickly. However, taking the experience of Kretschmer et al. into account, with the rapid antigen testing leading to unnecessary quarantine and high economic burden, the novel rapid and inexpensive testing methods are therefore valuable.

To deal with these difficulties in detecting the SARS-CoV-2, the Integrated Mobile Container PCR Laboratory (IMCPL) unit was developed in China, which was a standard PCR laboratory established inside a walk-in container and can be quickly set up at any convenient locations to carry out the large-scale diagnostic testing.

Two main characteristics of the IMCPL make this medical unit more suitable for diagnostic detection than the traditional laboratories in the event of major public health emergencies. First, the IMCPL unit is extremely sturdy and mobile (Fig. 1 ). The square rectangle cabin is 17.5 m in length, 3 m width, and 3 m height, built using steel plates of 3 mm thickness with each part further reinforced to ensure the safety during transportation. In order to be deployed rapidly, the IMCPL unit can be conveniently carried and transported by using a logistics 17.5 m semi-trailer (Fig. 1A), enabling the long-distance and cross-regional laboratory support facilitated in a short time. Second, the installation requirements of the IMCPL unit are minimal. The IMCPL unit can be installed quickly at any convenient sites under most circumstances in less than 2 h with the availability of both water and electricity.

Fig. 1

The IMCPL units in China. (A) An IMCPL unit loaded onto a truck and later transported to Korla, Xinjiang. (B) An IMCPL unit being unloaded from the truck and installed locally. (C) An IMCPL unit set up at the Hongkong West Road in Qingdao, Shandong, next to the buildings of Guoxin Haitian Center. (D) An IMCPL unit installed at the Qingdao Navy Special Service Sanatorium, Qingdao, Shandong.

To assess the operating efficiency of the IMCPL unit, we carried out the tests in the IMCPL unit at the Shandong Provincial Hospital in China. The processing speed of the laboratory completing the sample testing depends largely on the proficiency of the personnel members and the operational efficiency of the supporting equipment. In our study, several skilled medical laboratory technicians performed individually a load test on the supporting equipment installed in the IMCPL unit, including the hot thermostat pan (used to inactivate viruses), nucleic acid extractor, and the fluorescent quantitative PCR analyzer (Fig. 2 A-C). The experimental procedure was performed according to the manual of the kits.

Fig. 2

The high operating load of the IMCPL unit. (A) Nucleic acid extractor. (B) PCR analyzer. (C) Dry thermostat. (D) A statistical chart of the time required by a skilled laboratory doctor to complete the steps of COVID-19 testing. (E) Statistical graph of the number of specimens tested vs. number of PCR analyzers operated.

The results showed that it took a skilled technician ∼35 min to complete the sample inactivation, 20–40 min to finish the nucleic acid extraction, and 90–120 min to run the nucleic acid amplification (Fig. 2D). These results showed evidently that the operation efficiency on the equipment was greatly improved in the IMCPL unit in comparison to normal process performed in a regular molecular laboratory. Overall, it took a skilled technician 135–195 min to complete the detection of viral nucleic acid in a batch of 96 samples in the IMCPL unit.

In order to maintain the high work efficiency, we organized four working shifts every day with a group of staff members replaced and the instruments disinfected every 6 h. The results showed that an IMCPL unit equipped with 12 PCR analyzers completed the nucleic acid detection of ∼8000–10,000 clinical samples within 24 h (Fig. 2E), demonstrating evidently the enhanced SARS-CoV-2 detection capability of the IMCPL unit in a high-throughput manner.

It is worth noting that under the condition of low incidence, IMCPL can be used as an independent laboratory configured by the hospital to complete the daily testing work. The Shandong Provincial Hospital began to operate the IMCPL unit on January 7, 2021, with a total of 132,027 samples processed by August 14, 2021, significantly alleviating the workload pressure on the clinical laboratory at the hospital.

The large-scale SARS-CoV-2 screening is necessary to prevent the spread of the disease COVID-19, to help government make relevant public health policies, and to test people and their close contacts with a history of travel or residence in the epidemic areas. The IMCPL unit can be used as a reserve force for the health and epidemic prevention programs, ultimately reducing the unnecessary high positive rate and economic burden caused by the application of rapid antigen testing. Under the current unpredictable situations in many countries globally, the IMCPL unit could be used in combination with the local medical laboratories to eliminate the blind spots in the areas with epidemic.

Declaration of Competing Interest

The authors declare that no competing interests exist related to this submission.