1. Lab 13
Sweat Test

2. Introduction
A sweat test measures the amount of salt chemicals (sodium and chloride) in sweat to diagnose cystic fibrosis
Sodium and chloride are part of your body’s electrolyte balance, and combine to form the salt found in sweat.
They help regulate the fluid balance in your tissues.
Normally, sweat on the skin surface contains very little sodium and chloride. People with cystic fibrosis (CF) have 2 to 5 times the normal amount of sodium and chloride in their sweat.
Criteria for a positive sweat test in children (sweat sodium greater than 60 mmol/L and sweat chloride greater than 70 mmol/L)
child may need more than one sweat test to confirm a diagnosis of cystic fibrosis.
The sweat test is considered the gold standard for diagnosing CF.

3. Cystic fibrosis
Cystic fibrosis (CF), mucoviscoidosis, or mucoviscidosis of pancreas, is a life - threatening hereditary disease inherited as autosomal recessive and is characterized by:
Increased viscosity of mucous secretions, including pancreas, intestinal glands, tracheal, peritracheal, bronchial.
Thick mucus production, as well as a less competent immune system, cause mucus to build up and clog some of the organs in the body, particularly in the lungs and pancreas. When mucus clogs the lungs, it makes breathing very difficult.

5. It also causes bacteria (or germs) to stuck in the airways causing inflammation (or swelling) and infections which ultimately leads to lung damage.
Mucus also can block the digestive tract and pancreas causing stop of digestive enzymes from getting to the intestines.
Increased concentration of electrolytes especially Na and CL, in secretion of other gland notably (sweat glands, Parotid salivary glands, lachrymal glands).
Mucus also can block the digestive tract and pancreas causing stop of digestive enzymes from getting to the intestines. The body needs these enzymes to break down food, which provides important nutrients to help us grow and stay healthy.

7. Symptoms of cystic fibrosis (CF)
Thick, viscous mucus secretions in the lungs
Repeated infections.
Pale or clay colored Stools, foul smelling, or stools that float
meconium ileus is a typical finding in newborn babies with CF
Recurrent pneumonia
Chronic cough, possibly with blood streaking
Wheezing
Bronchitis
Repeated infections: The accumulation of sticky, thick mucus in the lungs creates a favorable environment for infectious microorganisms to inhabit and flourish.
Float = متقلب
meconium, is blocking the last part of the baby’s small intestine (ileum)
meconium (black sticky stool normally passed within 24 hours of delivery)  and your baby may also be reluctant to feed and may vomit a green fluid called bile which would normally pass through the bowel.
A tube will be passed through your baby’s nose into the stomach to drain away the bile (green fluid) that collects here. This reduces the risk of your baby vomiting and reduces discomfort.

8. Weight loss, failure to thrive in infants, abdominal swelling
Chronic sinusitis
Asthma
Weight loss, failure to thrive in infants, abdominal swelling
Excessive salt in sweat, dehydration
Failure of newborn to pass stool
Abdominal pain, flatulence
Fatigue
Changes in color and amount of sputum (material coughed up from the lungs)
flatulence : the accumulation of gas in the alimentary canal.

10. Fatty BM’s : Fatty Bowel Movements

11. Sweat Analysis

12. Two methods of sweat analysis are most frequently used:
1. Chloride concentration
The sweat chloride analysis is recommended as the diagnostic test for CF.
2. Conductivity measurement.
Sweat conductivity may be used to screen for CF.

13. Sample collection Earlier methods:
to stimulate the production of sweat including the use of humid high temperature room, and encasing the patient’s Body in plastic.

14. Current methods
1. A tiny amount of a sweat-stimulating liquid is applied to a small patch of skin on the arm or leg. 2. An electrode is then placed over the site & a weak electrical current stimulates the area. This is a painless procedure that may create a tingling or warm sensation. 3. After several minutes, the area is cleaned and sweat is collected for about thirty minutes, either into a plastic coil of tubing or onto a piece of gauze or filter paper. 4. The sweat obtained is then analyzed.

15. Procedure of the test Done on a baby's right arm or thigh.
With older child or adult, the test is usually done on the inside of the right forearm.
Sweat may be collected and
analyzed from two different sites.

16. One pad is soaked with a medicine called pilocarpine makes skin sweat.
Skin is washed and dried & then, 2 small gauze pads are placed the skin.
One pad is soaked with a medicine called pilocarpine makes skin sweat.
The other pad is soaked with salt water such as NaNO3.
The other pads called electrodes are placed over the gauze pads.
The electrodes are hooked up to an instrument that produces a mild electric current, which pushes the medicine into the skin.
Another testing method collects the sweat into a coil (macroduct technique).
Mutations in the CFTR gene disrupt the function of the chloride channel, preventing the usual flow of chloride ions and water into and out of cells.

17. The sweat test usually takes 45 minutes to 1 hour.

18. After 5 to 10 minutes, the gauze pads and electrodes are removed, then the skin is cleaned with water and then dried. The skin will look red in the area under the medicine-containing pad
A dry gauze pad, paper collection pad, or special tubing is taped to the red patch of skin. This pad is covered with plastic or wax to prevent fluid loss (evaporation).

19. The new pad will soak up the sweat for up to 30 minutes, then it is removed and placed in a sealed bottle. It is then weighed to measure how much sweat the skin produced, and it is checked to find out how much salt chemical (sodium and/or chloride) the sweat contains.
After the collection pad is removed, the skin is washed and dried again.
Then we measure Cl by automated or manual titration method and Na by flame photometry or ion exchange electrode.

20. A sweat test measures the amount of salt chemicals (sodium and chloride) in sweat. Generally, chloride (sweat chloride) is measured.
Sweat chloride
Normal Less than 40 (mmol/L)
Borderline –60 mmol/L.
Abnormal More than 60 mmol/L.
Abnormal (high) values: Usually mean a person has cystic fibrosis. Some people with cystic fibrosis have borderline or even normal sweat chloride levels

21. Thank you