Contributor: Adam Tyson, MD
Last Update: 8/6/2013
AmniSure tm is a rapid test for diagnosis of ruptured membranes (ROM). It detects the presence of placental alpha microglobulin-1 (PAMG-1) in cervical and vaginal secretions.
The test has shown sensitivity of 93-99% and specificity of 88-100% in published data, with PPV of 95-100% and NPV of 91-99%. This compares to sensitivity of 85%, specificity of 39% with PPV of 49% and NPV of 79 for conventional bedside testing.
The test can be used even in the presence of blood, as long as the sample is composed of less than 50% blood, or other contaminants.
Instructions for Use
A speculum is not required to perform the exam.
The test swab is inserted into the vagina to 2-3 inches depth and allowed to remain for one minute.
The swab is then placed in the developing solution for one minute. A test strip is then placed in the solution and left for 5-10 minutes. If PAMG-1 is present in the fluid, two lines will appear in the results area of the strip as early as five minutes after beginning the assay. If, after 10 minutes, only one line is present, the test is negative.
In our practice, the clinician will collect the swab and the assay will be performed in the laboratory.
Suggestions for Use
Although AmniSure can be used to detect ROM in any clinical situation, the test is significantly more expensive than conventional methods. Average cost is around $50 to purchase each test kit, with laboratory fees added to the charge billed to the patient or insurance payor.
Therefore, it is recommended that AmniSure not be used as the default method for diagnosis of ROM but only in cases when conventional testing has been performed and is not diagnostic.
Likewise, it should not be used in situations where clinical management will not be significantly changed by diagnosis of ROM, i.e. a patient being admitted for term labor.
Some examples of recommended uses are as follows:
- Diagnosis of ROM in cases where there is blood or other discharge in the vagina.
- To establish diagnosis in cases of equivocal or conflicting testing (nitrazine positive, but ferning absent).
- Patients transferred from another facility where testing for ROM conflicts with testing on evaluation here.
- In cases where the clinical history and related findings such as reduced AFI support the diagnosis of ROM but conventional testing is negative or non-diagnostic.
- Cousins LM, Smok DP, Lovett SM, Poeltler DM. Amnisure placental a microglobulin-1 rapid immunoassay versus standard diagnostic methods for detection of rupture of membranes. Am J Perinatol 2005;22:317–320.
- Lee SE, Park JS, Norwitz ER, Kim KW, Park HS, Jun JK. Measurement of placental a-microglobulin-1 in cervicovaginal discharge to diagnose rupture of membranes. Obstet Gynecol 2007;109:634–640.
- Tagore S, Kwek K. Comparative analysis of insulin-like growth factor binding protein-1 (IGFBP-1), placental alpha microglobulin-1 (PAMG-1) and nitrazine test to diagnose premature rupture of membranes in pregnancy. J Perinat Med 2010; 38: 1-4.
- Birkenmaier A, Ries JJ Kuhle J, Burki N, Lapaire N, & Hosli I. Placental a-microglobulin-1 to detect uncertain rupture of membranes in a European cohort of pregnancies. Arch Gynecol Obstet. 2012; 85(1):21-5.
- Albayrak M, Ozdemir I, Koc O, Ankarali H, Ozen O. Comparison of the diagnostic efficacy of the two rapid bedside immunoassays and combined clinical conventional diagnosis in prelabour rupture of membranes. Eur J Obstet Gynecol Reprod Biol. 2011 Oct;158(2):179-82.
- Abdelazim IA, Makhlouf HH. Placental alpha microglobulin-1 (AmniSure(®) test) for detection of premature rupture of fetal membranes. Arch Gynecol Obstet. 2012 Apr;285(4):985-9.
- Marcellin L, Anselem O, Guibourdenche J, De la Calle A, Deput-Rampon C, Cabrol D, Tsatsaris V. Comparison of two bedside tests performed on cervicovaginal fluid to diagnose premature rupture of