1.0 Sweat Chloride Collection

Message

SWCLT: Sweat Chloride Test
Includes:

SWCLC: Sweat Chloride collection Site
SWCLV: Sweat Chloride Volume
SWCL: Sweat Chloride (test value)

Test Code

1.0 SWCLT

Patient Preparation

Sweat collection procedures must be scheduled. Call 559-459-6542 to schedule patient for testing or complete and fax Outpatient Laboratory Requisition-Scheduled Tests.
Patient/guardian should be provided with procedure information that includes the possible risks of the procedure and patient preparation before specimen collection.
1. English Version: Information for Sweat Chloride Testing.
2. Spanish Version: Information for Sweat Chloride Testing
Patient Age:
1. Asymptomatic newborns with positive newborn screens should be at least 2 weeks of age, 36 weeks post conception, and weigh greater than 2 kg. before doing the sweat test.
2. Symptomatic newborns may be tested and evaluated as early as 48 hours after birth.
3. Children and adults may be tested at any time.
The preferred site for optimal collection is an area with a high density of sweat glands. Generally, the arms have a higher density of sweat glands then the legs.
1. For normal size infants, children and adults: The preferred collection site is the lower portion of the flexor aspect of the forearm.
2. For tiny infants: The preferred collection site is the upper portion of the flexor aspect of the forearm (near elbow) or upper arm.
3. For premature infants or if entire arm is too small: The inner thigh may be used.
Patient Notes:
1. The selected site must be free of breaks, fissures, or observable abnormalities of the skin with no signs of inflammation. It must also be wrinkle free and as hairless as possible. For adults, it may be necessary to shave the hair from the arm before starting collection procedure.
2. The sweat collection procedure should be performed on patients who are clinically stable, well hydrated, free of acute illness, and not receiving mineralocorticoids or topiramate (anticonvulsant drug).
3. Repeat sweat collection and analysis can be performed at any time.
4. Duplicate testing on the same day may be used to decrease the likelihood of inadequate specimens.

Instructions

Sweat Stimulation

Obtain Sweat Chloride Test Collection Worksheet to document all phase of collection as related to Patient Preparation, Collection and Post Collection steps.
Assemble equipment and all supplies listed in materials section.
Inspect electrodes and connect to inducer by pressing the plug into the jack on sweat inducer panel.
1. Engage positive/negative pins correctly.
2. Tighten the locking ring to secure connection.
Clean the selected skin areas:
1. Swab the selected area vigorously with the alcohol wipe.
2. Swab the selected area with plenty of purified water. For dark skin, rub vigorously.
3. Leave the area wet to ensure uniform contact with the Pilogel disc and to reduce the possibility of a burn.
Install Pilogel discs on both electrodes
1. Press firmly around disc for uniform, air free contact with electrode.
2. Small slivers of gel shaved off while installing is normal.
Attach the electrodes to the limb ensuring the electrodes are placed such that iontophoretic current never crosses the patient's trunk to avoid the possibility of current crossing the heart, resulting in cardiac depolarization.
1. Place each strap so stud on electrode protrudes through the rivet of the strap.
2. The hook portion of short tab is to be away from skin.
3. Secure electrode firmly so gel surface is flat against skin.
Activate Iontophoresis: Push control switch to RUN position and hold momentarily until the short beep.
1. Watch for CURRENT FLOW indicator to reach full brightness - approximately 20 seconds.
2. The indicator diminishes in brightness during last 5 seconds of iontophoresis as the current is brought to zero.
3. The current rises to 1.5mA during a 17 – 30 sec interval, remains constant for 5 minutes, then decreases in last 6 seconds.

Sweat Collection

Prepare Macroduct sweat collector during iontophoresis.
1. With gloves, remove Macroduct sweat collector from package.
2. Thread strap of suitable size through the slots so hook side of strap faces away from the collection surface. DO NOT TOUCH THE COLLECTION SURFACE.
Remove electrodes at completion of iontophoresis.
1. Remove negative (black) electrode first.
2. Clean exposed area of skin with purified water.
3. Mark around the Red electrode with alcohol base marker if needed -to ensure proper placement of the Macroduct sweat collector.
4. Remove the positive (Red) electrode.
Clean stimulated skin with purified water to remove salt.
1. Blot dry.
2. You should see distinct redness to skin under the red electrode.
< >attach Macroduct Sweat collector firmly to limb.Thread limb through the opening in the strap.
Apply the concave surface of the collector precisely over the skin contacted by the Pilogel disc.
Apply slight pressure to the collector then fold the end of the strap over and attach.
Hold collector in place, fold the other end of strap back around so it overlaps the previously folded end.
1. Overlap should be 3-4 cm. Verify collector is firmly attached and check periodically for displacement. Adjust if necessary.
2. Cover area with heel warmer and coban bandage to ensure firm contact.
The macroduct allows you to visually assess the sweat production by reference to the spiral tube calibration diagram. A 30 minute collection time usually yields 50-60 microliters (µL) of sweat and should be adequate.
1. Set timer for 30 minutes. After 30 minutes visually check the adequacy of specimen amount against the coil diagram.
2. Adequate specimen is 2 turns of the coil which equals approximately 19µL.
3. If specimen volume is close to but has not met the 19µL mark, allow another 15 minutes of testing to occur to bring to adequate volume.
4. Remove sweat sampler. While still attached to arm, remove the protective transparent cover by using the nippers and pry upward.
  1. Pull plunger back midway before inserting into tubing.
  2. Insert the blunt needle approximately 5 mm into open end of Macroduct microbore tubing using twisting motion OR Pull up 1 to 2 inches of the microbore tubing from the adhesive base before attaching tube to blunt needle of syringe. DO NOT SQUEEZE dispenser or syringe body or move the syringe plunger while attaching or in next step.
  3. Grasp tubing where attached to needle.
  4. Pull tubing away from collector body until completely uncoiled and extending outward from the point of attachment.
  5. Sever the tubing close to collection surface using nippers.
  6. Immediately expel the sweat into the cup and immediately install cover to protect specimen and to prevent evaporation. Label specimen container with small label, time and collector initials.
  7. Immediately deliver specimen along with Sweat Collection Test Collection Worksheet to Core Laboratory for specimen acceptability. NOTE: The analysis should occur shortly after collection, or within a few hours. If there is a significant delay between collection and analysis, the laboratory may store the sample up to 72 hours at refrigerator temperature.
    1. CLS will document volume on worksheet. Worksheet is placed in Specimen Collection Supervisor's mailbox for review.
  8. If specimen does not meet minimum requirement of 15µL, testing cannot be performed and collection must be repeated.

Post Collection Cleanup
1. Remove and discard the collection body.
2. Retain the strap.
3. Clean the electrode
  1. Remove and discard the Pilogel discs.
  2. Clean electrodes with purified water and wipe dry.
4. Clean instrument case and cable with damp cloth of 10% bleach or mild soap.
Remove linen from bed and clean mattress or phlebotomy chair with hospital approved disinfectant Clorox Healthcare Bleach Germicidal Wipes®.

Sweat Analysis:

Sweat specimen is delivered immediately to the Core laboratory for chloride analysis.

Clinical Significance

The quantitative measurement of chloride is sweat. It is used to confirm the diagnosis of Cystic Fibrosis (CF). With an incidence of 1:32000, CF is the most common life threatening genetic disease within the white population.

Newborns less than 1 month of age may be diagnosed with Cystic Fibrosis (CF) through newborn screen testing. However, the newborn screen may miss some cases and children and adults may present later with signs and symptoms of CF. Persons afflicted by the disease are prone to acute hyponatremia during hot weather. This occurs because of an abnormally high salt concentration of their eccrine sweat, ranging from three to five times higher than that of normal persons.

The “sweat test” is a critical element in the diagnosis of cystic fibrosis. The sweat test is composed of three separate, sequential procedures, (1) Sweat Stimulation, (2) Sweat Collection and (3) Sweat Analysis for chloride concentration.

Performing Laboratory
Collection at CRMC Outpatient Service Center
Testing at CRMC Laboratory

Additional Information
Sweat Chloride Information English
Sweat Chloride Information Spanish
Outpatient Scheduled Procedure Requisition

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.