• ACD or CPD—28 days

• Clotted whole blood—14 days

4. Use of hemolyzed samples Check the samples before use. Do not use hemolyzed samples

5. Sample used for newborns below

one year of age

A1 antigen is not fully expressed on the red blood cells of newborns below one year of age

6. Prozoning (zone of antibody

excess) or postzoning (zone of

antigen excess)

The antigen and the antibody should be present in optimal concentrations of the agglutination

to be seen properly. Check the sample volume and the reagent volume used. Both the sample

and reagent volume should be equal in slide test and a 5% suspension of cells should be

used in tube test. Ensure that there are no air bubbles while dispensing samples and reagents

Blood Banking (Immunohematology) 381

Anti-H Lectin

Problem: False positive results

Possible causes Solutions

1. Bacterial contamination (some bacteria

will agglutinate all red cell samples thereby

giving false positive results)

Check the reagents for turbidity. Extreme turbidity may indicate bacterial

contamination. Such contaminated reagents should not be used for testing

2. Particles of dust, debris, chemicals or

detergents on the slide or in the tube giving

non-specific agglutination

Clean and dry glassware should be used while carrying out the test

3. Peripheral drying or fibrin strands were

mistaken for agglutination in case of slide

test

The test should not be carried out directly under the fan. The vials should be capped

immediately after use. The results of the test should be read at 2 minutes not beyond

as drying may be interpreted as positive result

4. Excessive centrifugation in case of tube test Ensure that centrifugation is carried out for either one-minute at 1000 rpm or

20 seconds at 3400 rpm. Centrifugation should be adequate to produce a cell button

with a clear supernatant but without packing the cells so tightly that they are difficult to

dislodge

Each laboratory must calibrate it equipment at regular intervals

Problem: Hemolysis of red blood cells

Possible causes Solutions

1. Use of wet slides and tubes Wet glassware can cause hemolysis of RBC’s. Ensure that only dry glassware is used

for testing

Problem: False negative results

Possible cause Solution

1. Storage of antiseras at higher/lower

temperatures than specified

Reagents should be stored at 2–8°C when not in use

Thermal damage due to faulty storage may result in a loss of reactivity

Antibody activity decreases at lower temperatures

Do not freeze the reagents

2. Blood sample stored for too long Check the period of time for which the blood sample has been stored

Anticoagulated blood using various anticoagulants should be tested

within the below mentioned time period (when stored at 2–8°C)

• EDTA or heparin—2 days

• Sodium oxalate or sodium citrate—14 days

• ACD or CPD—28 days

• Clotted whole blood—14 days

3. Use of hemolysed samples Check the samples before use. Do not use hemolyzed samples

4. Prozoning (zone of antibody

excess) or postzoning (zone of

antigen excess)

The antigen and the antibody should be present in optimal

concentrations of the agglutination to be seen properly

Check the sample volume and the reagent volume used. Both the

sample and reagent volume should be equal in slide test and a 5%

suspension of cells should be used in tube test. Ensure that there are

no air bubbles while dispensing samples and reagents

12

Cerebrospinal and

Other Body Fluids

C H A P T E R

CEREBROSPINAL FLUID

Cerebrospinal fluid (CSF) is formed primarily in

ventricular choroid plexuses by a combination of both,

active process and ultracentrifugation. Concentrations of

sodium, chloride, magnesium and glutamine are greater

in CSF than in plasma, while concentrations of glucose,

potassium, calcium, cholesterol, uric acid, iron, thyroxine

and zinc are lower in CSF.

Normal Values for Lumbar CSF in Adults

Pressure 70–150 mm of water column

(patient lying on side)

Volume 90–150 mL

Specific gravity 1.006–1.008

Total solids 0.85–1.70 g%

Cells 0–8 lymphocytes/cu mm

Neutrophils and erythrocytes

absent

Protein 20–50 mg%

Of this

albumin is 50–70%

α1 globulin is 3–9%

α2 globulin is 4–10%

β globulin is 10–18%

γ globulin is 3–9%

fibrinogen is Absent

Sodium 144–154 mEq/L

Potassium 2.0–3.5 mEq/L

Chloride 118–132 mEq/L

pH 7.3–7.4

Creatinine 0.5–1.2 mg%

Cholesterol 0.2–0.6 mg%

Glucose 50–80 mg%

Glutamine 6–16 mg%

Iron 1–2 mg%

Thyroxine 0.1–0.2 mg%

Urea 6–16 mg%

Uric acid 0.5–4.5 mg%

Lumbar Puncture

Lumbar puncture needle is a long needle with a stylette

inside. Lumbar puncture is usually performed at L3-L4 or

lower to avoid damage to the spinal cord. In small children

the conus medullaris extends lower than in adults, so

puncture should be performed at L4-L5 or lower.

Indications

1. Detection and diagnosis of suspected meningitis,

subarachnoid hemorrhage, encephalitis, central

nervous system (CNS) syphilis, spinal cord tumor or

multiple sclerosis.

2. Differential diagnosis of cerebral infarction vs

intracerebral hemorrhage (almost 80% of latter show

blood or xanthochromia).

3. Introduction of anesthetics, radiographic contrast

media or drugs.