PRINCIPLE:

The fern Test, used in conjunction with the Nitrazine test, detects the leakage of amniotic fluid from the membranes surrounding the fetus during pregnancy. This phenomenon is in part due the fluid’s protein and sodium chloride content. A positive test shows the presence of fern-like patterns characteristic of amniotic fluid crystals.

 Premature rupture of the membranes may lead to fetal infection and subsequent mortality. The risk may be eliminated by induction of labor.

 MATERIAL NEEDED:

• Clean glass slide
• Microscope

 SPECIMEN:

Vaginal secretion from the posterior vaginal pool collected with a sterile swab. Do not touch the mucus plug in the cervix.

PROCEDURE:

1. Immediately after the collection, rub the swab against a glass slide, creating a very thin smear. Do not coverslip.
2. Allow slide to dry. Do not apply heat.
3. Using a microscope, examine the dried smear under low power without a cover slip. 
4. If present, the amniotic fluid crystallizes to form a fern-like pattern due to the relative concentration of sodium chloride, protein, and carbohydrates in the fluid.
5. If ferning is difficult to locate, examine all fields on the slide thoroughly.
6. Fern Test should performed in conjunction with the Nitrazine Test.
7. On the Log sheet.  Record:  Patient’s name, DOB, result of test, and initial the results. 

INTERPRETATION:

Report results as” Ferning test positive for amniotic fluid” or Fern Test negative for amniotic fluid”.

• If the Nitrazine Test and the Fern test is positive, probable membrane rupture has occurred.
• If the Nitrazine test is negative but the Fern test is positive, there is probable rupture of the membranes due to the Fern Test’s greater specificity.
• If the Nitrazine Test is positive but the Fern Test is negative, a second specimen should be collected and tested.

QUALITY CONTROL:

• Follow the procedural instructions exactly.
• There are no external (or internal) quality controls to be performed at the time of patient testing.
• At least one provider per site will participate in semi-annual resting provide through the Point-of-Care office.

REFERENCES:

1. Addison, Lois Anne. Laboratory Medicine, July 1999 p 451
2. Fern Test (Amniotic Fluid Crystaization Test) CIOLA Guide to simple Laboratory Testing February 1998.
3. Oregon Health & Science University point-of-Care Fern Test Procedural manual.
4. Urinalysis and Body Fluids , Karen Munson Ringsrud, Lean Jorgenson Linne, Mosby Inc. St. Louis, Missouri
5. Body Fluids Laboratory Examination of Amniotic, Cerebrospinal, seminal, Serous & Synovial Fluids  Carl R. Kjeldsberg, Joseph A. Knight,  Second edition. American Society of clinical Pathologist  Press, Chicago

PLACED INTO SERVICE: October 2,  2005

SUPERSEDES PREVIOUS PRACTISES.