PROVIDER FREQUENTLY ASKED QUESTIONS

• Upper Respiratory
  • 15 viral targets
  • 10 bacterial targets
  • SARS-CoV 2
• STI
  • 6 targets

Turnaround time varies by testing type. For more information, reach out to your Gravity sales representative or email salesoperations@gravitydiagnostics.com  

Covid and Upper Respiratory Testing

• Samples must be received in the lab within 7 days and can be kept at room temperature. Saliva can be received in the laboratory within 4 weeks.
• Upper respiratory samples are collected using a nasopharyngeal swab.

STI Testing

• Samples must be received in the lab within 7 days in a grey-top preservative tube or 3 days in urine collection cups and can be kept at room temperature.
• STI panel samples require swabbing the patient’s genitalia or through urine collection (dirty catch)

T-Spot Testing

• T-Spot samples must be received in the lab within 52 hours of collection and MUST be kept at room temperature
  • Refrigerated samples or samples sent on ice will result in a rejection of the sample
• T-Spot samples are whole blood samples collected and stored in a lithium-heparin tube.
  • Samples are later isolated to obtain PBMCs (peripheral mononuclear blood cells)

QFT Testing

• QFT samples must be received in the lab within 56 hours of collection and MUST be refrigerated (4-8°C)
  • Samples sent at room temperature will result in a rejection of the sample
• QFT samples are whole blood samples collected and stored in a lithium-heparin tube.
  • Samples are later incubated and spun down to obtain plasma.

• Covid
  • After repeating, the sample did not have enough DNA.
    • This is usually due to improper collection.

• T-Spot
  • While interpreting results: 
    • The count for the negative control (nil spot count) was >10 spots 
    • The positive control was <20 spots AND the result was negative (Panel A and/or Panel B ≤4 spots) 
    • There was severe background staining and spots were not able to be counted. 
  • Invalid results are uncommon (<1%) and may be related to the immune status of the individual being tested. They may also be related to several technical factors, potentially resulting in high background, low mitogen, and high nil results, including: 
    • Inappropriate blood storage conditions 
    • Delay in sample transport 
    • Patient specific conditions 
    • Laboratory error 
  • Invalid results are not clinically interpretable and retesting by collecting another sample is recommended. 
  • Upon retesting, if the test result remains Invalid, other diagnostic tests and/or epidemiologic information should be used to help determine the TB infection status of the patient. 

While interpreting results: 

• Panel A or Panel B spot counts are equal to 5, 6, or 7 spots. 
• When a Borderline result is obtained, retesting by collecting another sample is recommended.
  • In a large multi-center study by King et al., most Borderline results, 79.8%, resolved as clearly Positive or Negative upon retesting. 
  • This study also demonstrated that 23% of Borderline results were Positive on retesting, concluding that the Borderline category is clinically relevant and useful in maintaining test sensitivity. 
• Upon retesting, if the test result remains Borderline, other diagnostic tests and/or epidemiologic information should be used to help determine the TB infection status of the patient. 

Invalid results cannot be interpreted due to the failure of the test’s positive and/or nil (negative) control. 

A Borderline result is a valid test where the spot count is too close to the established test cut-off to classify the result as Positive or Negative. 

When a sample is cancelled due to a white blood cell count <1.8, retesting by collecting another sample is recommended. 

A count of at least 1.8 is needed to perform the test and obtain accurate results.