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pH DETERMINATION USING NITRAZINE  (NitraTEST™) PAPER
for the DETECTION OF AMNIOTIC FLUID
 

 

PRINCIPLE                            Nitrazine paper is used to detect small quantities of amniotic fluid in vaginal secretions.  Premature rupture of the membranes before onset of labor may lead to fetal infection and subsequent mortality.  The risk is largely eliminated by induction of labor.

 

 

CLINICAL UTILITY                Evaluate whether to induce labor following rupture of membranes

 

SPECIMEN                            Vaginal secretions from the posterior vaginal pool. 

                                                Do not touch swab or pH paper to the mucus plug in the cervix.

                                                Test sample immediately after collection.

 

INTERFERENCES                1.  The nitrazine test is highly sensitive but not very specific.  Most studies report a 5% false-positive rate and a 1% false-negative rate.

2.      False-positive results may occur from specimen contamination due to heavy vaginal discharge, blood, cervical mucus, semen, alkaline urine, and soap.

3.      False-negative results can be produced by prolonged rupture of membranes (longer than 24 hours) or when only a small quantity of fluid has leaked.

 

NORMAL RANGE                  pH 4.5 to 6.0:  Negative for detection of amniotic fluid

                                              pH 6.5 to 7.5:   Positive for detection of amniotic fluid

 

COMPUTER CODES            Not applicable

 

QUALITY CONTROL            UMHS sequesters a large volume of Nitrazine paper and an initial quality control check is provided by the Department of Pathology Point-of-Care Services.  Certified pH buffers at two levels (4.0 & 7.0 respectively) are tested and/or Urine Alta Diagnostic Positive/Negative controls are used to verify pH levels at 4.0 to 7.5.  Documentation of quality control testing is maintained at the Department of Pathology-POC Services, Nursing Quality Control Improvement (Linda Potter) and Material Services Management (Tracy Buford). 

 

CALIBRATION                       Not applicable


 

 

PROCEDURE                        Gloves must be worn during the testing process to prevent exposure to bodily fluids. 

                                                1.   Tear off  approximately 1-1 ½ ” piece of NitraTest paper.

2.      Apply patient sample from swab onto the NitraTest paper.

NOTE:  1) Sample may also be collected using a dry sterile glove prior to cervical check. Obtain sample of vaginal secretions on the finger of the glove.   2) Sample may be obtained by direct application of the pH paper to the blue underpad when leaking fluid is copious.

3.       Immediately match the color of the strip to the closest color on

dispenser color chart. 

 

CALCULATIONS                   None

 

REPORTING                         If the Nitratest paper color is yellow to olive green, the corresponding pH is 4.0-6.0 and the test is NEGATIVE for amniotic fluid.

                                                If the NitraTest paper color is blue-green to deep blue, the corresponding pH is 6.5 to 7.5 and the test is POSITIVE for amniotic fluid.

 

REAGENTS                           NitraTest™ (Phenaphthazine Paper) (Range: 4.5 – 7.5)

`                                               Store at room temperature. Avoid excessive heat.

                                                Protect against exposure to acid or alkaline fumes before use.

Stability:  2 years after opening dispenser or manufacturer's
expiration date (whichever is shortest).

 

REFERENCES                      NitraTest™ (Phenaphthazine Paper), Bristol-Myers Squibb Company, package insert.

 

                                                Oregon Health & Science University Health Care System website:

                                                www.ohsu.edu/pathology/POC/procedures/phamniotic.html

               

 





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