dry and retest

5. Test results are correct but reporting may be wrong Check and verify final report correctly

6. Test interpretations are wrong Results should be interpreted as per test protocol

Agglutination = Positive

No agglutination = Negative

7. Drying of the reagent on slide Do not read results beyond 2 minutes

Do not perform the test directly under a fan

8. Male urine used as negative

control to check the working of

the kit

Do not use male urine as negative control as it will give false positive results

Since the hormones, protein and salt composition of male urineis different

and foresight being a direct test system is calibrated to yield accurate results

on male urine. Use the negative control provided with the kit or use known

negative female urine

Problem: False Negative Results

Possible causes Solutions

1. Wrong sample used Collect, label the samples appropriately and test accordingly

2. Sample stored for a long period of time 0.01%

should be used as preservatives. The samples can

then be stored

Specimens should be tested preferably within 12 hours of collection

Should a delay in testing occur, thimerosal 0.001% or sodium azide. at 2–8°C

for up to 72 hours

3. Reagent may have deteriorated due to thermal

damage

Avoid exposure of the reagents to high temperatures. Store at 2–8°C. Do not

freeze

4. Prozoning due to hCG levels above 250 IU/mL (In

pathological conditions such as choriocarcinoma

and hydatidiform mole)

In such cases, the sample should be diluted and used. Check the patient’s

history

5. Serum is being used as specimen Use only urine and not serum as specimen.

6. Sample drop size insufficient Ensure that the sample is dispensed using dispensing pipette provided.

Ensure that there are no air bubbles while dispensing the sample.

7. Reagents not brought to room temperature before

testing

Bring all reagents to room temperature before testing.

8. Presence of detergent on the slide Wash thoroughly with water and retest

Pregnancy Tests 423

Problem: False Positive Results

Possible causes Solutions

1. Presence of trophoblastic and non-trophoblastic neoplasms

such as choriocarcinoma and hydatidiform mole

Check the clinical history of the patient

2. The flow properties of the nitrocellulose membrane are partially

affected leading to the nonspecific movement of partially

aggregated gold-sol particles

Check the device/dipstic pouch for pinholes and observe the

dessicant for any color change. The results of the test should be

correlated with clinical findings

Problem: Delayed Positive Results

Possible causes Solutions

1. Urine samples were tested immediately after removing from

the refrigerator

Bring the urine samples to room temperature before testing

Problem: False Negative Results

Possible causes Solutions

1. Inadequate quantity of sample used for testing Dispense exactly 2 drops of the sample using the dropper provided

with the kit

2. The kit is exposed to very high temperatures leading to the

deterioration of the antibodies coated on the device/dipstick

Store the kit at 4–30°C when not in use

3. Turbid or contaminated urine samples used for testing Do not use contaminated urine samples. In case there is a delay in

testing urine samples can be stored at 2–8°C up to 72 hours. Turbid

samples should be centrifuged before testing

4. Highly diluted samples or samples of very early pregnancy used

for testing

Highly diluted samples or samples of very early pregnancy may not

contain representative levels of hCG. In such cases, if pregnancy is

suspected, the test should be repeated with first morning urine after

48–72 hours after the initial test

Problem: Invalid Results

Possible causes Solutions

1. Pinholes or defect in the pouch. The nitrocellulose membrane

has lost its flow properties due to the absorbance of moisture

Check the pouch for pinholes and also check the color of the

dessicant (silica gel) accompanying the pouch

A change in color from deep blue to white/pink indicates absorbance

of moisture. In such cases, discard the test device and rerun the test

using a fresh device

2. The device/dipstick is removed from the refrigerator and tested

immediately before attaining room temperature. This leads

to the hydration of the sites on the nitrocellulose membrane

thereby adversely affecting its flow properties

The test device/dipstick should be brought to room temperature

before being tested

RAPID FORMATS

Device/Dipstick

Clue

424 Concise Book of Medical Laboratory Technology: Methods and Interpretations Problem: False Positive Results

Possible causes Solutions

1. A number of other conditions including trophoblastic

and non-trophoblastic neoplasms such as hydatidiform

mole, choriocarcinoma cause elevated levels of hCG

Check the clinical history of the patient, before diagnosing for pregnancy

2. The flow properties of the nitrocellulose membrane are

partially affected leading to the nonspecific movement of

partially aggregated gold-sol particles

Check the device/dipstick pouch for pinholes besides also note color

changes if any,