The AL-SENSE Test Is Reliable for Detection of Second Trimester Amniotic Fluid
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The AL-SENSE comprises a regular panty-liner and
is worn as any other hygienic panty-liner. Inside the
panty-liner the AL-SENSE contains one strip of (color)
indicator that is sensitive to pH levels. The indicator
strip reacts immediately to any contact with amniotic
fluid or other vaginal discharge of pH 5.2 or greater.
Observing a change in the color of the pH indicator in-
dicates either a leak of amniotic fluid or a urine leak.
The indicators were placed in a drying box and observed
to determine the stability of the stain.
During amniocentesis performed for medical reasons
(primarily age over 35 years), between 18 and 23 weeks
of gestation, 0.5 ml of amniotic fluid, of the 30 ml usu-
ally drawn, were used for this study.
Two volumes of amniotic fluid, 100 µl and 400 µl,
were dripped onto two AL-SENSE panty liners num-
bered 1 and 2, respectively. After five minutes the indi-
cator strip was removed from the AL-SENSE and the
strips were placed in the drying units.
The color status was recorded from both panty-liners
immediately, after 5 and 10 minutes, and then every 10
minutes for the first 30 minutes and within 1, 2, 6 and 12
hours after removing the indicator strip and placing it in
the drying unit.
3. Statistical Analysis
Statistical analyses were performed using SAS® v9.1
(SAS Institute, Cary N.C., USA). Descriptive statistics
are presented in a table. Study results are presented as
counts or percentages together with a 95% exact bino-
mial confidence interval when relevant.
4. Results
Fifty (50) women were enrolled in the study; 49 (98%)
completed it. One patient was excluded due to a protocol
deviation.
The distribution of gestational age is presented in Ta-
ble 1; most women were in their 18th -19th week of ges-
tation.
One hundred percent of samples in both volumes
(95% CI: (92.75% - 100%)) changed color from yellow
to blue within five minutes and the color remained stable
Table 1. Distribution of gestational age by weeks.
Gestational Week N %
16 1 2.0
17 3 6.1
18 16 32.7
19 21 42.9
20 5 10.2
21 1 2.0
22 1 2.0
23 1 2.0
Total 49 100.0
throughout the twelve hour follow-up period. Initial in-
dicator color change did not occur at time 0 for all the
samples. In the 100 μl subgroup 7 of the 49 samples, or
14.3% (95% CI: (5.94% - 27.24%)), had a delayed color
change and in the 400 μl subgroup 1 of 49, i.e. 2.04%
(95% CI: (0.05% - 10.85%)), showed a delay in color
change.
5. Discussion
In the present study the AL-Sense panty-liner was found
to be very sensitive and changed its color in response to
a very small amount of second trimester amniotic fluid
obtained at amniocentesis. The color change was stable
for 12 hours, the time determined in advance as the
completion of the study. So far, the validity of the
AL-Sense panty liner has been proven in clinical studies
in diagnosing premature rupture of membranes in the
third trimester [1-3]. However, the effectiveness of this
test had not been tested in second trimester pregnancies.
This study utilized amniotic fluid obtained during
amniocentesis. Therefore, the effectiveness of this test
should be verified in a clinical setting, as the color of the
panty-liner may change in reaction to vaginal secretions
when infections that cause elevated pH are present (as
stated by the manufacturer). Nevertheless, Mulhair et al.
[3] found that women with positive high vaginal swabs
did not differ significantly and nine women with positive
high vaginal swab had a negative test (no color change).
The high pH level of amniotic fluid (7.42) even at
very early stages of pregnancy [4], the ability of the
panty-liner to detect it, even in very small amounts (100
µl), and the long term stability of the stain makes it a
very useful tool in diagnosing cases with premature
rupture of the membranes in the second trimester. This
period of pregnancy may be associated with significant
management dilemmas due to the high percentage of
fetal, neonatal and maternal complications with PROM
at that time [5-7]. The high sensitivity of this test in
clinical studies (100%) makes it very helpful in reassur-
ing patients that membranes have not ruptured.
A drawback of this test is its low specificity; hence,
when the test is positive the diagnosis should be verified
by other means. However, in this study, as we dripped
amniotic fluid directly on the panty-liner and there was
no contact with vaginal discharge or other fluide, we did
not include a positive/negative control.
Another possible use of this test is in patients experi-
encing post-amniocentesis fluid leakage. Since most of
these cases may be followed expectantly [8,9] the test
can be used to indicate cessation of amniotic fluid leak-
age (when a positive test become negative).
In conclusion, the panty-liner is effective in the sec-
ond trimester of pregnancy and can be used at that time
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