New requirements for molecular micro waived testing

Karen Lusky

September 2019—Four new checklist requirements for waived molecular-based microbiology tests have been added to the CAP point-of-care testing, limited service laboratory, and immunology accreditation program checklists, as part of the 2019 checklist edition released this month.

“The CAP has decided to improve patient care by providing additional safeguards that wouldn’t necessarily be performed otherwise,” says Bobbi Pritt, MD, MSc, DTM&H, chair of the CAP Microbiology Committee and professor, Mayo Clinic Alix School of Medicine.

Dr. Pritt and other members of the Microbiology Committee have noticed that even though the new cartridge-based waived molecular tests are self-contained, and the risk for nucleic acid leakage and contamination is low, nucleic acid contamination can occur. They have seen false-positive and -negative results, even with the purportedly low-risk molecular tests. Although the tests are waived, “we feel like there is still quality assurance and quality control that should be performed around them, as a best patient practice, knowing that this will be going beyond what the basic requirements may be,” says Dr. Pritt, who is director of Mayo’s clinical parasitology lab and co-director, vector-borne diseases laboratory services.

The committee was asked what requirements from the microbiology checklist should be made part of the POC testing checklist, and they worked with members of the Checklists and Point of Care Testing committees to make the selection. “It was a nice collaboration between our three committees,” Dr. Pritt says, “trying to use all of our different CAP expertise to decide what is applicable, what’s doable, what applies to day-to-day testing in a point-of-care setting.” They modified the four requirements “to be relevant to the point-of-care testing environment.” (The microbiology checklist can be used for both waived and nonwaived testing.)

The first waived molecular tests became available within just the past few years, says Amy Karger, MD, PhD, vice chair of the CAP Point of Care Testing Committee and medical director, West Bank Laboratory, University of Minnesota Health. “Since this is new technology, we have to adapt our checklists to reflect the different risks that come with molecular testing that aren’t seen with immunoassay testing.” Those who perform the testing must be educated about the risks for false-positives, she says.

The first new checklist requirement, POC.08675 Quality Monitoring Statistics, calls for written procedures to monitor for the presence of false-positive results (owing to nucleic acid contamination, for example) for all molecular microbiology tests. The note says, “Examples of this may include review of summary statistics (eg, monitoring percentage of positive results relative to current local and regional rates and increased positive Strep results above historical rate within a run or over multiple runs), performance of wipe (environmental) testing, review and investigation of physician inquiries, and use of process controls to minimize risk of contamination.”

Molecular platforms amplify genetic material from an organism, and because of that amplification step, Dr. Karger says, “you just need a little bit of material to contaminate a sample and create a false-positive.” Environmental contamination is a worry in POC testing, says Sheldon Campbell, MD, PhD, a member of the Checklists Committee, “where neither the staff nor the environment is set up for contamination control.”

If one patient’s swab is placed on a counter and it contaminates the counter surface, and another patient’s swab is then placed on the same counter, the second swab could pick up genetic material from the first swab. If the first patient was highly positive, the result for the second patient who might be truly negative will be a false-positive, which is why, Dr. Karger says, the first checklist requirement cites wipe testing in the note.

Wipe tests, like any procedure, must be well thought out and require skill to be done well, says Dr. Campbell, professor of laboratory medicine at Yale School of Medicine. “You wipe potentially contaminated surfaces and put the swab into your molecular test to see if you are getting positives from your environment as opposed to from patients.”

A point-of-care coordinator or supervisor who is observing and overseeing the staff’s workflow should determine whether to do wipe testing, Dr. Karger says, though it’s preferable to teach the best practice of not putting exposed samples where they could deposit genetic material. “If you have robust procedures in place where something like that wasn’t happening, then perhaps you wouldn’t feel like you needed to do wipe testing as a routine part of the process. That said, I do think occasional checks with wipe testing is a good idea.” If a clinic found that it was seeing a much higher rate of positives, Dr. Karger says, then wipe testing would be part of the investigation to identify the source of the contamination.

A test could become contaminated if people are administering influenza immunizations and a vial of influenza vaccine leaks onto the area where influenza PCR testing is performed, Dr. Pritt says. Testing is often performed in a small area, in which the same counter might be used to prepare vaccines. “We want to raise awareness that those types of activities should be done in separate areas,” she says. “These aren’t just little boxes they can put on their countertop and put in a sample and get a result and not really think about it. They have to think about the entire process from start to finish.”

They have to understand, too, the risks associated with a false-positive. When patients pre­sent with respiratory tract symptoms and fever, Dr. Campbell says, the potential diagnoses include bacterial pneumonia, flu, congestive heart failure, and other conditions. If a molecular flu test is a false-positive owing to contamination, “providers may not work up other problems. They could treat the person for flu and send them home when the person has a bacterial pneumonia.” Or a patient with a false-positive result could be treated unnecessarily, with Tamiflu perhaps. “That medication has side effects,” Dr. Karger says.

The second new checklist requirement, POC.08690 Specimen Handling Procedures, calls for written procedures to prevent specimen loss, alteration, or contamination during collection, transport, processing, and storage. Collection, processing, and storage must follow the manufacturer’s instruction, the note says, and limit the risk of preanalytical error. “For example,” the note says, “there must be a procedure to ensure absence of cross-contamination of samples during processing/testing for respiratory specimens tested at the point-of-care that may be sent to the laboratory for further testing. It is also essential to follow the manufacturer’s instructions for the handling of wastes (eg, used test cartridges) to prevent contamination.”

Dr. Pritt says the CAP wants point-of-care labs to think of their entire workflow and have procedures in place to prevent loss, alteration, or contamination. “If they are going into that specimen and taking out an aliquot, are they doing that in a sterile manner? How do they prevent someone from contaminating that specimen?” Someone without laboratory training may not think of those things, she notes.

The cartridges contain amplified DNA that can cause false-positives, Dr. Campbell says, so it’s critical to make sure they are disposed of in medical waste without harming the cartridge.

The third new checklist requirement, POC.08715 Safe Specimen Handling/Processing, says there must be written policies for safely handling and processing samples from patients with suspected infection due to avian influenza, SARS, Ebola, or similar emerging pathogens. The note says the policies may be part of an institution’s plan but that the plan must address point of care specifically.