the test should be repeated with a fresh specimen

collected after a week.

ELISA PREGNANCY TEST

(Vectra from Tulip Group of Companies)

Introduction

Vectra pregnancy test is a rapid, visual, qualitative, enzyme

immunoassay for the determination of human chorionic

gonadotropin (hCG), a marker for pregnancy in urine/

serum.

Principle

Vectra pregnancy test utilizes the principle of sandwich

enzyme immunoassay, with a unique mono-antibody

combination specific against hCG present in urine/serum.

The patient urine/serum specimen is allowed to react

with the monoclonal antibody directed against hCG, coated

on the microtiter wells and the monoclonal antibodyenzyme conjugate complex. If hCG is present in the test

specimen, antibody-hCG-antibody-enzyme complex will

be formed on the surface of the microtiter well. Washing

the well under running tap water will clear off the unbound

complex and the unreacted conjugate. Incubating the

well with substrate reagent results in development of

blue color. The intensity of the blue color is proportional

to the concentration of hCG present in the urine/serum

specimen. Visual comparison of the intensity of the blue

color with test specimen well as against the positive control

well indicates the concentration of hCG greater than or

equal to 25 mlU/mL of hCG in the test specimen.

DIPSTICK ICT PREGNANCY TEST

(Clue from Orchid Biomedical Systems)

Clue one step pregnancy test is a rapid, self-performing,

qualitative, two-site sandwich immunoassay for the

determination of human chorionic gonadotropin (hCG), a

marker for pregnancy, in urine specimens.

Summary

Human chorionic gonadotropin (hCG), a glycoprotein

hormone secreted by viable placental tissue during

pregnancy, is excreted in urine approximately 20 days after

the last menstrual period. The levels of hCG rise rapidly

reaching peak levels after 60 to 80 days.

The appearance of hCG in urine soon after conception

and its rapid rise in concentration makes it an ideal marker

for the early detection and confirmation of pregnancy.

However, elevated hCG levels are frequently associated

with trophoblastic and non-trophoblastic neoplasms and

hence these conditions should be considered before a

diagnosis of pregnancy can be made.

Clue one step pregnancy test detects the presence of

hCG in urine specimens, qualitatively, at concentrations

as low as 10 mlU/mL in less than 5 minutes.

Principle

Clue one step pregnancy test utilizes the principle of

immunochromatography, a unique two site immunoassay on a membrane. As the test sample flows through

the membrane assembly of the dipstick, the colored antihCG-colloidal gold conjugate complexes with the hCG in

the sample. This complex moves further on the membrane

to the test region where it is immobilized by the anti-hCG

coated on the membrane leading to formation of a pinkcolored-band which confirms a positive test result. Absence

Pregnancy Tests 417

of this colored-band in the test region indicates a negative

test result. The unreacted conjugate and unbound complex

if any move further on the membrane and are subsequently

immobilized by the anti-mouse antibodies coated on the

membrane at the control region, forming a pink band. This

control band serves to validate the test results.

Reagents and Materials Supplied

Each individual pouch contains :

1. Dipstick: Membrane assembly predispensed with antihCG antiserum-colloidal gold conjugate and anti-hCG

antiserum and anti-mouse antiserum at the respective

regions.

2. Desiccant pouch.

Storage and Stability

The sealed pouches in the test kit may be stored between

4–30°C till the duration of the shelf life as indicated on the

pouch.

Note

1. For in vitro diagnostic use only. Not for medicinal use.

2. Do not use beyond expiry date.

Specimen Collection and Preparation

Though random urine specimens can be used, first

morning urine specimen is preferable as it contains the

highest concentration of hCG. Specimens should be

collected in clean glass or plastic containers. If testing is not

immediate, the urine specimens may be stored at 2–8°C for

up to 72 hours. Turbid specimens should be centrifuged or

allowed to settle and only the clear supernatant should be

used for testing.

Test Procedure and Interpretation of Results

1. Collect urine specimen in a clean test tube. Ensure that

only sufficient quantity of the specimen is collected to

allow submerging the red area of the dipstick (About

1 cm high).

2. Bring the sealed pouch to room temperature, open

the pouch and remove the dipstick. Once opened, the

dipstick must be used immediately.

3. Dip the red area of the dipstick in the urine specimen

submerging only the red area.

4. Observe for the release of the colloidal gold complex

on the membrane. This would be seen as a pink

moving front on the membrane and could take 10 to

15 seconds to appear depending upon the sample.

5. Remove the dipstick and place horizontally on a flat

surface. Alternatively the dipstick may be left to stand

in the specimen for the entire duration of the test

ensuring only the red area is left submerged in the

specimen.

6. At the end of 5 minutes read the results as follows:

 Negative: Only one pink-coloredband appears on the dipstick.

 Positive: Two distinct pinkcolored bands appear on the

dipstick.

7. The test should be considered invalid if neither the

test band nor the control band appears. Repeat the

test with a new dipstick ensuring sufficient dip time

as mentioned in point no. 4.

Limitation of the Test

1. A number of conditions other than pregnancy

including trophoblastic and non-trophoblastic

neoplasms such as hydatidiform mole, choriocarcinoma, etc. cause elevated levels of hCG. Such

clinical conditions must be ruled out before diagnosis

of pregnancy can be made.

2. Highly dilute urine specimens and specimens from

very early pregnancy may not contain representative

levels of hCG. If pregnancy is still suspected, repeat

the test with first morning urine after 48–72 hours.

3. As with all diagnostic tests, the results must be

correlated with clinical findings.

DEVICE ICT PREGNANCY TEST

(Clue from Orchid Biomedical Systems)

Specimen Collection and Preparation

Though random urine specimens can be used, first

morning urine specimen is preferable as it contains the

highest concentration of hCG. Specimens should be

collected in clean glass or plastic containers. If testing is not

immediate, the urine specimens may be stored at 2–8°C for

up to 72 hours. Turbid specimens should be centrifuged or

allowed to settle and only the clear supernatant should be

used for testing.

Test Procedure and Interpretation of Results

1. Bring the sealed pouch to room temperature, open

the pouch and remove the device. Once opened, the

device must be used immediately.

2. Dispense two drops of urine specimen into the sample

well’S’ using the dropper provided. Refrigerated

specimens must be brought to room temperature prior

to testing.

418 Concise Book of Medical Laboratory Technology: Methods and Interpretations 3. At the end of 5 minutes read the results as follows:

 Negative: Only one coloredband appears on the control

region ‘C’.

 Positive: In addition to the

control bands, a distinct

colored-band also appears

on the test region T.

4. The test should be considered invalid if neither the test

band nor the control band appear. Repeat the test with

a new device.