glassware for turbidity. Ensure that clean and dry glassware and micropipettes are used

8. Improper storage condition To maintain the sensitivity and performance of the reagent, avoid thermal stress due to

leading to reagent precipitation exposure to high ambient temperature thereby causing precipitation, ensure that the

reagent is stored at the recommended temperature

9. Contaminated/wet micropipette Ensure that clean and dry tips are used for retrieving the reagent

tips used for retrieving the reagent

10. Improper plotting of calibration curve The calibration points must be plotted correctly for getting the exactly values of test

fibrinogen levels

11. Significant levels of heparin and elevated

levels of fibrinogen degradation products

(FDP) in the patient plasma

Contd...

Clinical Hematology: Bleeding Disorders 315

12. Clotting times of patients on anticoagulant The history of the patient must be taken carefully to determine the anticoagulant used

therapy depends on the type and dosage and FDP levels in the patient plasma as well as the time lag between the specimen

of anticoagulants and also on the time collection and the last dose of anticoagulant

lag between specimen collection and the

 last dose of anticoagulant

Problem: Shortened Clotting Time

Possible causes Solutions

1. Broken glassware allowing silica Ensure that broken glassware is not used for testing purposes

to trigger the clotting reaction

2. With fibroscreen, fibrin gels These gels are not firm, extrude considerable serum, and tend to slide

may form in the plasma with a on the sidewalls of the tilted test tube. Careful comparison of such gels

fibrinogen concentration below with a firm clot with normal plasma as a control will eliminate the

normal possibility of confusion.

Fibrinogen Degradation Products (D-Dimer) Estimation XL-FDP®

Problem: False Positive Results

Possible causes Solutions

1. Markedly lipemic, hemolyzed Avoid using lipemic, hemolyzed and contaminated samples for testing

 and contaminated serum samples

could produce nonspecific results

2. Drying of reagent on the slide Do not read results beyond 3 minutes. The test should not be carried out directly under

the fan

3. Presence of dust or debris on Dust or debris could be misinterpreted as agglutination, therefore, only clean and

the glass slide used dry glass slides must be used for testing

4. Latex particles contaminated with Care must be taken to see that the reagent dropper tip does not touch the sample

positive control/positive sample taken on the slide during dispensing of the reagent

5. Dried latex particles observed Immediately after performing the test, transfer the contents of the reagent dropper back

in the latex reagent into the reagent vial

• During slide test with negative control Ensure that no reagent is left behind in the dropper.

Close the cap of the reagent vial properly and store it back at 2–8°C

• In the dropper of the vial (due to freezing Do not freeze the reagent vial

  of the latex reagent during storage)

• Improper dispensing of the

 entire reagent from dropper

6. Activation of coagulation system Elevated levels of plasma XL FDP may be expected to occur in such

with subsequent microvascular conditions. Note the clinical history of the patient before arriving at a

fibrin deposition and lysis has final diagnosis

been reported in diverse clinical

conditions such as trauma, surgery,

inflammation and malignancy

Contd...

316 Concise Book of Medical Laboratory Technology: Methods and Interpretations Problem: Delayed Agglutination

Possible causes Solutions

1. Cold reagents are used for Bring all reagents and samples to room temperature before commencing the testing

 testing procedure

Problem: False Negative Results

Possible causes Solutions

1. Serum is used as test specimen Always use plasma as test specimen for performing the test

2. The reagent may be damaged Check the performance of the latex reagent using known positive samples, if the latex reagent

due to microbial contamination is working then the positive control may have deteriorated

or exposure to extreme

 temperatures

3. Weak agglutination is difficult Shake the latex reagent well before use to disperse the latex particles uniformly and improve

to interpret the test readability

4. Excess sample dispensed Dilute the plasma and check for agglutination. If no agglutination is observed with the

leading to prozoning neat sample but agglutination is observed with the diluted sample, then it may be due to

prozoning. Determine the titer. Dispense exact amount of sample as mentioned in the package insert

5. Samples stored for a long period Fresh samples are preferable for testing, however; samples can be stored for up to a

of time are used as specimens week at 2–8°C

6. In PE, if the clots are of small

size. The amount of D dimmer

released from very small clots

may be diluted by the circulation

7. Patients with stabilized clots The clinical history of the patient must be taken consideration to determine the D dimmer

and not undergoing active levels in the patient

fibrin desposition and plasmin

activation may not give detectable D

dimmer elevations

8. In case of hereditary, acquired

deficiency and dysfunction of

fibrinogen

9. If the conclusion of false Run the test with a third kit to validate results

negative result has been arrived

at by comparison with another

kit, then this other kit could be

giving a false positive reaction

Problem: Positive Control Giving Negative Reaction

Possible causes Solutions

1. The positive control may have Check the performance of the latex reagent; using known positive samples, if the latex

deteriorated due to contamina- reagent is working then the positive control may have deteriorated

tion or exposure to extreme

 temperatures

11