Consensus standard operating procedure for collection of tongue swabs for TB diagnostics
Charlotte Ahls, Anura David, Adithya Cattamanchi, Margaretha de Vos, Karen Heichman, Adam Penn-Nicholson, Lesley Scott, Amy E Steadman, Lindsey Turnbull, Alfred Andama, Gerard Cangelosi, Midori Kato-Maeda, Alaina Olson, Rachel Wood, Kris Weigel
Tongue swab
dorsum tongue
Mycobacterium tuberculosis
tuberculosis
swab collection
tuberculosis tongue swab
Abstract
This standard operating procedure (SOP) outlines the methodology for the collection of tongue swabs for subsequent testing of tuberculosis molecular assays that require a dry swab as input material.
Before start
Timing of collection: Confirm participant has met NPO (nothing by mouth) criteria for 30 minutes preceding tongue swab collection. Confirm that the participant has not expectorated sputum, brushed their teeth, used mouthwash or tobacco products, or consumed food/liquids. If the participant has engaged in any of these activities in the preceding 30 minutes, delay the tongue swab collection until the 30-minute window has passed. For studies also collecting a sputum sample for Xpert MTB/RIF Ultra or culture, tongue swabs should be collected before sputum collection.
Steps
Collection Method
Prior to collection, label transport tube as per standard practice.
Place the collection tube in an upright position in a tube rack. Loosen the cap on the collection tube to facilitate ease of handling during swab insertion. Keep the cap on the collection tube until it is time to insert the swab into the tube.
Open the swab package carefully at the shaft end, as indicated on the packaging. Only handle the swab by the portion of the shaft farthest from the swab head. To avoid sample contamination, at no point during sample collection should you, touch or handle the portion of the shaft between the swab head and the breakpoint.
Collect the Sample as per Section "Swabbing technique" .
Immediately after collection, remove the cap of the storage tube.
Carefully snap the swab handle off at the 30mm breakpoint. Ensure that the cap of the collection tube will seal without obstruction (top of remaining swab shaft sufficiently below tube cap).
Dispose of the remaining swab handle as per local guidelines for handling biological waste.
Seal the tube cap securely. Place the collection tube into a leak-proof biohazard bag and place in refrigerator or cool box (2-8°C) immediately after collection.
If testing is done off site, the samples should be sent to the laboratory on the same day and no later than 24 hours after collection.
Swabbing Technique
Tongue swabs should be collected as followed by trained personnel:
General Swab Handling: To avoid potential contamination of the sample, take care to only handle the swab by the portion of the shaft farthest away from the swab head. Do not handle the swab shaft between the breakpoint and the swab head, as this portion will be snapped off into the tube for sample storage/testing.
Tongue swabbing technique: Using a back-front and left-right motion, swab (brush) from the back of the top of the tongue and as far back as possible without creating a gag reflex (about ¾ of the visible tongue dorsum). Using a timer, swab for 30 seconds, with a focus on the back area of the tongue. Apply enough pressure while swabbing to slightly bend the stem of the swab. Constantly roll (rotate) the swab until the timer is up. All sides of the swab head should be covered with material from the tongue and appear wet.
Transport and Storage
All swabs should be transported to the testing laboratory on cold chain at 2-8°C.
Swabs can be stored for long term at-80°C.
