Lab Test Procedure : Patient Instructions for the Iontophoresis Sweat Collection Procedure
An electric current introduces the sweat inducing drug (Pilocarpine Nitrate) into a selected clean skin area. A macroduct sweat collector is placed on the patient=s limb and covered to insure that it is airtight. After 30 minutes, the tubing is plugged, and the macroduct sweat collector is removed from the patient=s limb. It is sealed in a 0.5 ml micro centrifuge tube with flip top cap, labeled with an appropriate patient label, and then sent to the laboratory to be analyzed for chloride concentration.
Wescor Macroduct Sweat Collection System with automatic voltage setting of 1.5mA
- Give the patient the fluids he or she normally drinks and encourage an extra bottle/cup at least one hour prior to the appointment time. These can be formula, milk, water, juice, breast milk, or other drinks. The patient should eat normally and may take all medications the day of the test.
- This test and a test for which the patient cannot eat or drink must be done on different days.
- Do not use creams, oils, or lotions on arms (arms and legs if a newborn) for 24 hours prior to your appointment.
- Bring warm clothes – a coat and hat and/or blanket for the patient to wear during the test.
- The patient should not be feeling ill the day of the test, with a fever, bad cold, or flu. If the child is ill, please call the laboratory to reschedule at 330-543-8573. If a chronic cough is present with no symptoms to suggest a bad cold or the flu, the test can be performed.
* Call the patient 24-48 hours prior to the appointment and verify that the patient is aware of the patient instructions.
* BE FAMILIAR WITH ANOTES@ AT THE END OF THIS PROCEDURE BEFORE PERFORMING IONTOPHORESIS. DO THIS PROCEDURE ON TWO ARMS OR TWO LEGS. TIME EACH SIDE FOR 30 MINUTES SEPARATELY.
- Please document/complete the following prior to testing:
A. Ask the parent if they received the parent information sheet. If they did not, please provide it to them.
B. Complete the questionnaire (Sweat Test Log) regarding potential QNS factors.
C. Outpatients - Assess patient for compliance with criteria. If any of the following conditions exist, it is preferable to reschedule the test. If the parent/guardian feels the physician would be concerned about the delay, then call the physician and discuss the situation. If there is a desire to proceed even though the patient falls in the criteria listed below, let the physician know that you must contact pulmonology for authorization. Contact Dr. Omlor by calling the CF Center (x33900) and letting the front desk know that you have been told to contact him ASAP to make a decision regarding the performance of a Sweat Chloride test. The conditions are as follows:
- the patient is noticeably running a fever
- the parent/guardian says they have been sick in the previous 24 hours
- he patient is less than 48 hours old
- the time is beyond the 1100 cut-off
- the patient is on open oxygen
- the patient was fasting for another test
D. For Inpatients, the physicians will follow a Policy for ‘Obtaining a Sweat Chloride on an Inpatient’. If the lab gets a request for a test to be performed on an Inpatient, they will verbally verify that the ordering physician has followed the above policy and then proceed to arrange for a time to perform the test.
Set the collection room thermostat to a temperature to maintain warmth in the room during sweat collection.
Explain the procedure to the family/patient.
Assemble equipment and supplies.
A. Clinical Laboratory Reagent Water (CLRW).
B. Gauze pads or cotton balls, alcohol pads.
C. Sweat Inducer, Velcro straps (red, black, and blue), electrode set, macroduct sweat collector, sweat dispenser, pilogel disc, and blunt end #22 needle and 1 ml syringe.
Inspect electrodes and connect to inducer.
A. Clean electrodes with water and dry. Check wires and insulation for cracks or fraying.
B. Engage the electrode plug with the jack on the sweat inducer panel. Tighten the locking ring to secure the connection.
Clean the selected skin areas. ONLY LOWER ARMS OR UPPER LEGS ARE TO BE USED AS COLLECTION SITES.
A. Vigorously swab the entire area where the red and black straps will be placed with alcohol or soap, then thoroughly rinse with plenty of CLRW.
B. Dry the entire area well with clean gauze.
Install Pilogel discs on both electrodes (press firmly to achieve a uniform, air-free contact).
*Do not use discs which have been frozen or cracked.
*Do not use discs with a diameter significantly smaller than that of the electrode (shrinking can occur if discs dry out).
Using a dropper, wet the contact surface of each pilogel gel disc with a small drop of water.
Place the electrodes on the limb. On the arm, place the red electrode as low as possible while still maintaining full contact. On the upper thigh, place the red electrode as close to the knee as possible. Always place both electrodes on the same side of the body. Do not place electrodes across the chest or on opposite limbs. The selected site must be free of breaks or observable abnormalities.
A. Make sure the stud of the electrode protrudes through the rivet of the strap with the hook tab facing upward, away from skin.
B. Secure the electrode firmly so the gel is pressed flat against the skin and the area is slightly indented. There should be moderate pressure to minimize discomfort, but do not tighten so much as to crush the gel discs.
A. Push control switch to run. You will hear a short beep. Indicator will reach full brightness in five seconds. The stimulation process will last for 5 minutes. If a continuous alarm sounds, move the control switch to Stop and correct the fault condition.
Prepare macroduct sweat collector during Iontophoresis.
A. Open the macroduct collector bag and while still in bag, place the macroduct strap through one slot so that the Ahook@ portion faces away from the collection surface.
DO NOT TOUCH CONCAVE COLLECTION SURFACE.
Remove electrodes at completion of Iontophoresis.
A. At completion (5 minutes), a short beep will sound, and the inducer will turn itself off.
B. Remove Negative (black) electrode. Clean area with CLRW and dry well.
C. Remove the Positive (red) electrode and clean the skin with CLRW and dry well. There should be a distinct redness under the red electrode.
Immediately attach macroduct sweat collector firmly to limb. Apply the concave surface of the macroduct collector precisely on the area of iontophorectic stimulation (center of the reddened area). Thread the strap through the large opening and tighten until you can see a slight puckering of the skin through the area where the strap attaches to the unit. Do not tighten so much as to cause major discomfort or unusual color in the lower portion of the limb. If patient=s parent or guardian asks you to loosen the strap because they feel it is too tight, validate the appropriateness of the tightness, and then make a second effort to convince them that it must be tight or there is a much greater chance of a QNS collection. If they still insist the straps be loosened be sure to note this on the patient sweat test log. Wrap the Macroduct collector with a 2 to 3 inch wide piece of stretched Parafilm which will remain on the arm during the 30 min collection.
Have the child put on their coat and hat and/or wrap them up in a blanket. Have the patient and parent remain in the collection room in the Outpatient Lab, during the 30 minute collection period to avoid any disturbance or delay in removing the collecting device. The room should be comfortably warm. Adjust the thermostat if needed or shut the door to maintain warmth.
At ten (10) minutes, examine the collection coil for sweat. If sweat yield does not appear to be good, a heel warmer can be placed above the collector and secured with more stretched Parafilm. A heel warmer can also be used at the beginning of the collection if the skin is unusually dry.
* Sweat must be collected for exactly 30 minutes.*
Remove and store sweat sample. (This procedure must be carried out while the macroduct collector is still firmly strapped to the limb.)
A. Employee should be wearing gloves and face protection before removing sweat from the collector.
B. Attach blunt #22 needle to the 1 ml syringe and pull back the plunger as far as it will go without pulling the plunger out of the body of the syringe. Set aside.
C. When it is time to remove the collector, the limb with the collector should be extended on a flat surface. If the patient is uncooperative ask a parent or co-worker for help.
D. Unwrap the Parafilm while keeping firm pressure on both outer edges where straps attach to the collector unit using your forefinger and thumb.
E. Continue to press collector very firmly against skin for a few seconds to transfer residual sweat to the spiral tube. Use the needle to pry off the cover plate.
F. While maintaining continual downward pressure on the collector unit, attach the needle/syringe assembly to the open end of the coiled tubing. Insert approximately 1/4 to 3/8 inches into the tubing.
G. With the syringe assembly attached, gently lift the tubing off of the sticky surface of the collector unit until fully extended.
H. Lay syringe assembly and tubing on the counter next to the patient=s limb and using clean blunt nose scissors (wiped with CLRW water), snip the tubing as close as possible to the base of the collector unit.
I. You can now release the pressure on the collector unit.
J Gently straighten the kinked end of the tubing and insert it 1/4 to 3/8 inch deep into the 0.5 ml micro centrifuge tube securing it there with your fingertip.
K. Dispel the collected sweat into the tube by depressing the syringe plunger as far as possible until all the sweat is dispensed. Immediately close the flip top cap. Label with appropriate patient label. Include employee number, time, and left or right side collection. Wrap the top with Parafilm.
L. Remove and discard the tubing. Do not discard the needle/syringe assembly. If the needle gets any overflow sweat inside clean with CLRW water and let dry.
M. Remove collector unit from patient=s limb and discard.
N. Immediately send samples to Chemistry for analysis.
O. Keep the straps.
A. Remove and discard Pilogel discs.
B. Clean electrodes with alcohol, then CLRW water and wipe dry.
- Do not attempt iontophoresis on a patient who is receiving oxygen by an open delivery system. Iontophoresis can be performed on patients receiving oxygen by face mask or nasal cannula.
- Do not place electrodes across the chest or on opposite limbs.
- Try to pick a site that is free of breaks, fissures, and observable abnormalities in the skin. The area must be as wrinkle-free and hairless as possible.
- Use fleshy areas away from bone and tendons to make proper macroduct collector to skin interface.
- Never attach an electrode to the skin without pilogel. Direct skin-to-metal contact will burn the patient.
- Iontophoresis should not be performed on patients less than 48 hours old.
- Important note
Allergic reactions to pilocarpine iontophoresis are extremely rare but can occur. If an area of diffuse inflammation and hives occurs after the iontophoresis and/or collection, immediately discontinue the procedure and do not assay the sweat. Call the patient=s physician and ask for instruction. If the physician is not available and the parent is particularly concerned, the patient could be seen in the Emergency Department. Please escort them to the desk and notify a lab manager so all Emergency Room billing can be canceled.
2. Velcro straps are only used as long as they are clean and dry. When they come in contact with non intact skin or when they are soiled, they are discarded.
3. Complete the information in the Sweat Test Log.
- Macroduct Sweat Collection System Instruction/Service Manual; 2004
- Sweat Testing: Sample Collection and Quantitative Analysis; Approved Guideline - Third Edition; C34-A3, Vol. 29, No 27, December 2009.
- Macroduct Collection device insert, June 13, 2008.
- Addition of note number 2 at the suggestion of Lorie Lerner, Director of Infection Control at CHMCA, during her annual inspection of the laboratory=s iontophoresis procedure.
- CLSI Document C3-A4, Vol. 26, No. 22, Preparation and Testing of Reagent Water, 2006.
- Evaluation of our sweat testing procedure by Vicky A. Legrys, Dr,A., CLS (NCA), MT(ASCP), Professor, UNC. November 2006.
- Site visit to Columbus Children=s to observe their iontophoresis procedure. June 2010.