Water deprivation

Sample type: -

Plasma.

Urine sample.

Uses: -

Measure how much urine is made and how concentrated it becomes when no water is given to a patient for a certain amount of time.

Precautions: -

1. The test should be initiated at 10 PM at which time serum and urine specimens are collected for the determination of sodium and osmolality.

2. The patient should also be weighed at this time.

3. No oral intake is allowed until the test is terminated.

4. urine should be collected hourly for measurement of volume and determination of osmolality.

5. This test should not be performed if the patient’s initial serum osmolality is >295 mOsm/kg.

Interfere factors: -

• Diabetes.

• Drugs that can affect urine output

Pre-analytical errors: -

• Patient not following the tests protocol.

• Wrong identification of the patient and sample.

Corrective actions: -

• Proper instruction of the test to the patient.

• Correct labelling of the sample.

Post-analytical errors: -

• Delivering results takes a long time.

• Mixing between patient’s results.

Corrective actions: -

• Delivering results on time.

• Correct storing of the sample.

Reference range: -

Normal values range from 275 to 295 mmol/kg.