Type of test Fluid analysis

Normal findings

 Sodium values in children

 Normal: < 70 mEq/L

Abnormal: > 90 mEq/L

Equivocal: 70-90 mEq/L

Chloride values in children

Normal: < 50 mEq/L

Abnormal: > 60 mEq/L

Equivocal: 50-60 mEq/L

Test explanation and related physiology

Patients with cystic fibrosis (CF) have increased sodium and chloride contents in their sweat. This forms the basis of this test, which is both sensitive and specific for CF. CF is an inherited disease characterized by abnormal secretion by exocrine glands in the bronchi, small intestines, pancreatic ducts, bile ducts, and skin (sweat glands). Normally, sodium and chloride travel in and out of the body’s cells, helping to maintain electrical neutrality and water balance. This movement occurs because a protein called the cystic fibrosis transmembrane conductance regulator (CFTR) instigates the passage. CFTR serves as a channel, letting chloride and sodium out of cells and into the surrounding fluid and also reducing sodium absorption. CF is caused by a mutation in each of the two copies of the CFTR gene (one copy from each parent). With two mutations, the CFTR protein may be dysfunctional or totally absent. The increased sodium, chloride, and water stay in the cells and cause thick secretions in the ducts of multiple organs. Increased concentrations of these electrolytes exist in the sweat of patients with CF. Sweat induced by electrical current (pilocarpine iontophoresis) is collected, and its sodium and chloride contents are measured. The degree of abnormality is no indication of the severity of CF; it merely indicates that the patient has the dis ease. In most circumstances just the chloride needs to be tested. Sodium usually mirrors chloride.

This test can also be used to screen children or siblings of CF patients for the disease. Almost all patients with CF have sweat sodium and chloride contents two to five times greater than nor mal values. In patients with suspicious clinical manifestations, these levels are diagnostic of CF.

Sweat direct measurement testing is the preferred confirmatory test for CF. Measuring the sweat conductivity by using a commercial analyzer is easier and is most used as a screening test for CF.

Molecular genotyping for the CFTR gene is used for carrier identification, prenatal diagnosis in at risk pregnancies and newborn screening programs for CF.

Sweat testing is complex, the results are dependent on technique, and there is significance of a positive or negative result. Therefore, only selected, well trained individuals should perform this test.

Procedure and patient care

Before

* Explain the procedure to the patient and parents.

* Tell the patient and parents that no fasting is required.

During

• Note the following procedural steps:

 1. For iontophoresis, a low-level electrical current is applied to the test area (the thigh in infants and the forearm in older children).

 2. The positive electrode is covered by gauze and saturated with pilocarpine hydrochloride, a stimulating drug that induces sweating.

3. The negative electrode is covered by gauze saturated with a bicarbonate solution.

4. The electrical current is allowed to flow for 5 to 12 minutes.

 5. The electrodes are removed, and the arm is washed with distilled water.

6. Paper disks are placed over the test site with the use of clean, dry forceps.

 7. These disks are covered to obtain an airtight seal, preventing evaporation of sweat.

 8. After 1 hour the cover is removed. The paper disks are transferred immediately by forceps to a weighing jar and sent for sodium and chloride analysis. The disks can be inserted into a commercial analyzer to measure sweat conductivity.

• Note that an experienced technologist performs the sweat test in approximately 90 minutes in the laboratory or at the patient’s bedside.

* Inform the patient that the electrical current is small and no discomfort or pain is generally associated with this test.

 After

* Initiate extensive education and counseling for the patient and parents if the results indicate CF.

Abnormal findings

- CF

اخر الاخبار

اخبار العتبة العباسية المقدسة

معهد القرآن الكريم النسويّ يعقد الجلسة الرابعة من مسابقة فضة القرآنية

العتبة العباسية المقدسة تهيّئ الصحن الشريف استعدادًا لمهرجان رحمة للعالمين الدولي الأوّل

بمشاركة عددٍ من الطلبة.. المجمع العلمي ينظّم دورة مختصّة بالتجويد في محافظة الديوانية

العتبة العباسية المقدسة تنشر لافتات احتفائية بذكرى المولد النبوي الشريف

المزيد

الآخبار الصحية

هل من الآمن شرب القهوة على معدة فارغة؟

تحذير: مرض السكري يسرق طاقة قلبك

حقيقة صادمة.. لماذا يجب أن تتوقف عن شراء الجزر الصغير؟

بعد عمر الستين.. توقيت وجبة الإفطار مؤشر على صحتك

المزيد

الآخبار التكنلوجية

تركيب مقعد الطفل بأمان في سيارتك: دليل كامل وسهل

مليار مليار عملية في الثانية.. ألمانيا تدشن الحاسوب الفائق

أخيرا.. إنستغرام يصل رسميا إلى آيباد

حل يثير جدلا طبيا.. حقنة قادرة على إخفاء الشيب من رأسك ؟!

المزيد

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