Fluid Analysis

Sample for Fluid Analysis

• The fluid for the analysis  are:
  1. Ascitic fluid.
  2. Pleural fluid.
  3. Pericardial fluid.
  4. Amniotic fluid.
  5. Cerebrospinal fluid.
  6. Semen analysis.
  7. Cervical mucus test.
  8. Joint fluid (synovial fluid).
  9. Sweat chloride test.
  10. Urine analysis.

Indications for Fluid Analysis

1. To diagnose the cause of the fluids.
2. This could be therapeutic.
3. To diagnose the diseases.

Precautions for Fluid Analysis

• The fluid analysis should be done immediately to prevent false results due to cellular or chemical deterioration.
• Follow precautions if there is a delay in the testing of fluid.

Pathophysiology of Fluids 

1. Effusions from the abdomen, pleura, pericardium, and joints are classified into exudate and transudate.
   1. Exudates are caused by inflammatory, infectious, or neoplastic diseases.
   2. Transudates are caused by venous congestion, hypoproteinemia, and fluid overload.
2. Some of the fluids are analyzed to diagnose the disease, like sweat for cystic fibrosis.

Various Procedures to get fluids are:

1. Lumbar puncture for CSF.
2. Amniocentesis to get fluid from the uterus.
3. Pericardiocentesis for pericardial fluid.
4. Thoracentesis for pleural fluid.
5. Paracentesis for the peritoneal fluid.
6. Arthrocentesis for the fluid from the joints.

The fluid analysis includes:

1. Gross appearance.
2. Specific gravity
3. Total protein
4. LDH level.
5. Total cell count.
6. Microscopic examination for the differential count.
7. Cytospin For the cytological examination.
8. In the case of CSF, the glucose level is estimated.
9. In some cases, AFB or Gram stain is done.
10. Fluid analysis is to diagnose the etiology of fluid formation, or sometimes it may be therapeutic.

Therapeutic advantages of Fluid Analysis:

1. Fluid aspirated from the pleural improves ventilation and oxygenation.
2. Fluid from the Peritoneum relieves the pressure and ease of breathing and eating.
3. Fluid aspirated from the joint relieves the pain and function.
4. Fluid aspirated from the pericardial cavity improves diastolic filling and cardiac output.

Difference between various fluids:

Test	Exudate	Transudate	Chylous
Appearance	cloudy	clear	cloudy to milky
Color	variable	pale yellow	pale yellow to milky
Cell count	>1000	<1000	>1000
DLC	poly → MN cell	lympho	poly → MN cells
Triglycerides	<60 mg/dL	<60 mg/dL	>110 mg/dL
Total protein	>3.0g/dL	<3.0g/dL	>3.0g/dL
Fluid protein/serum TP	>0.5	<0.5	>o.5
Fluid LDH/serum LDH	>0.6	<0.6	>0.6

TP = Total protein

MN = Mononuclear cells.

Comparison of Transudate and Exudate:

Parameter (Characteristic features)	Transudate	Exudate
Appearance	Pale yellow	Yellow (inflammatory) Red (hemorrhage) Brown (bilirubin)  or cloudy
Protein	<3 g/dL	>3 g/dL
Fluid: serum protein ratio	<0.5	>0.5
Fluid: LD ratio	<0.6	>0.6
Specific gravity	<1.016	>1.016
WBC	Absent	Increased
LDH	Normal  <200 IU/L	Increased >200 IU/L
Glucose	Normal (equal to serum level)	Less or equal to serum
Pleural fluid cholesterol	<60 mg/dL	>60 mg/dL
Pleural fluid: serum cholesterol  ratio	<0.3	>0.3
Pleural fluid: bilirubin ratio	<0.6	>0.6
Fibrinogen	No clot	Clots are seen
Spontaneous clotting	Negative	May see clot formation
Cell count	300 to 1000 /cmm	>1000 /cmm
WBCs	Few lymphocytes	Many polys >25%
RBCs	Few	Variable
Differential	Mononuclear cells predominate <25% neutrophils	>25% neutrophils

• Please see more details in fluid part 3.

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