Limitations

• The Xpert MRSA NxG test performance has not been evaluated in patients less than two years of age.
• As with many diagnostic tests, results from the Xpert MRSA NxG test should be interpreted in conjunction with other laboratory and clinical data available to the clinician, and should be used as an adjunct to nosocomial infection control efforts to identify patients needing enhanced precautions. Results should not be used to guide or monitor treatment for MRSA infections.
• A positive test result does not necessarily indicate the presence of viable organisms. It is, however, presumptive for the presence of MRSA.
• A negative test result does not exclude the possibility of nasal colonization because test results may be affected by improper specimen collection, technical error, sample mix-up, or because the number of organisms in the sample is below the limit of detection of the test.
• The Xpert MRSA NxG test provides qualitative results. No correlation can be drawn between the magnitude of the Ct value and the number of cells in an infected sample.
• Mutations or nucleotide polymorphisms in primer or probe binding regions may affect detection of new or unknown MRSA variants resulting in a false negative result.
• Because the detection of MRSA is dependent on the quantity DNA present in the sample, reliable results are dependent on proper specimen collection, handling, and storage.
• The Xpert MRSA NxG test may generate a false positive MRSA (MRSA DETECTED) result when testing a nasal specimen with a mixture of organisms containing both methicillin-resistant coagulase-negative Staphylococcus and an empty cassette SA.
• The Xpert MRSA NxG test may generate a false negative result (MRSA NOT DETECTED) in the event of a co-colonization that contains both methicillin-resistant Staphylococcus aureus (MRSA) and an empty cassette Staphylococcus aureus (SA). This may occur in rare cases when the titer of an empty cassette SA organism is substantially higher than that of the MRSA organism.