Common Formulae of Diagnostic Laboratory: Introduction, List of Formulae, and Description

Introduction of Common Formulae of Diagnostic Laboratory

The ‘Common Formulae of Diagnostic Laboratory’ title is really useful who are involved in the Department of Pathology and Laboratory Medicine tests reporting as well as students who are related to this branch of health science. The author has already suffered not getting this type of huge collection of formulae in his earlier carrier of service and thus he decided to generate this type of knot. In this cluster, you will get common formulae of Hematology, Biochemistry, Histopathology, Microbiology, Serology/Immunology, Molecular Biology, Biostatistics, and other Health Related fields.

Required Common Formulae of Diagnostic Laboratory

Required Common Formulae of Diagnostic Laboratory
Fog. Required Common Formulae of Diagnostic Laboratory

List of Common Formulae of Diagnostic Laboratory

  1. Hemoglobin
  2. Red blood cells count
  3. Packed Cell Volume/Haematocrit
  4. Mean Cell Volume
  5. Mean Cell Haemoglobin
  6. Mean Cell Haemoglobin Concentration
  7. Color Index
  8. White Blood Cell Count
  9. Platelets count
  10. Reticulocyte count
  11. Absolute Eosinophil Count
  12. % Eosinophils
  13. VLDL
  14. LDL
  15. 24 Hours Urinary Protein Calculation
  16. Sperm count
  17. Micro Loop Factor


Haemoglobin Calculation

Haemoglobin (gm%) =(Optical Density of Test x Standard Concentration)/Optical Density of Standard

Red Blood Cells Calculation

Total RBC / mm3 (μL)×106  =       

  (Number of Cells Counted x Dilution factor)/(Area counted (1/5)x Depth of Fluid)

Where dilution: 1:200

Area counted: 80/400=1/5 ( 4 Corners and 1 center of R zone)

Depth of fluid=1/10= 0.1

= N x 200 / (1/5x 0.1)

=N x 10000

Mean Cell Volume (MCV) Calculation


(PCVx 10 )/RBC in Millions

e.g. PCV=45%

RBCs count=5.0 m/cu mm (μL)



90 cu mm

Mean Cell Haemoglobin (MCH) Calculation


(Haemoglobinx10)/RBCs in millions

e.g. Hb=14 g/dl

RBC count: 5.0 m/cu mm (μL)



= 28 pg

Mean Cell Haemoglobin Concentration (MCHC) Calculation



Where suppose, Hb=14 g/dl



=14/40 x 100


Color Index Calculation

Color Index= Hb%/RBC%

For example

Hb= 12 g/dl

RBC count: 4.3 m/cu mm

Hb%= 100 x 12/14.5=83%

RBC %=100 x 4.3/5.0= 86%

Color Index: 83/86=0.97

Normal Color Indec: 0.85-1.15

White Blood Cells (WBCs) Count

Total WBCs / mm3 (μL) =

(Cells counted x Dilution factor)/ 4 (Area Counted)x Depth of factor

Where Dilution: 20

Area Counted: 4

Dilution: 0.1

=(N x 20 )/ (4 x 0.1)

=Number of Cells Counted x 50

Platelet Count

Total Platelets / mm3 = (Cells counted x Dilution factor)/ (Area Counted x Depth)

Where Dilution: 200

Area counted: 1 (R zone of Neubauer Chamber)

Depth of fluid: 0.1

(Nx 200)/ (1x 0.1)

=  Number of Cells Counted x 2,000

% Reticulocytes= (No of Reticulocytes Counted x 100)/ Number of red blood cells counted (red cells in 15 fields)

Normal Range-

  • Adults: 0.2-2%
  • Infants: 2 -6%

Absolute Eosinophil Count

Two types of chambers are available to count absolute eosinophils and they are-

  1. Fuch-Rosenthal counting chamber
  2. Improved Neubauer Chamber

The formula for Absolute Eosinophil Count by Fuch-Rosenthal counting chamber

Total number of Eosinophils=(Number of cells counted x 10 x 5)/16

=Number of cells counted x 3.125

Where dilution=10

Area of fluid: 16

Depth of fluid: 1/5

The formula for Absolute Eosinophil Count by Improved Neubauer counting chamber

Total number of eosinophils, cu mm= (Number of cells countedx10)/0.9

Where dilution=10

Area of fluid=9

Depth of fluid=0.1

% Eosinophils Calculation

% Eosinophils= (Absolute count x 100)/Total WBC count

Very-low-density lipoprotein (VLDL) cholesterol

VLDL= Triglyceride/5

Low-density lipoprotein (LDL) cholesterol Calculation

LDL = Total Cholesterol – VLDL – HDL

24-hour Urinary Protein Estimation

24 hours Urinary Protein=urinary protein (mg/dl) x total urinary volume

Normal urine protein in adults is less than 150 mg within a 24-hour period.

 Sperm Count

Sperms/ ml of semen


    (Number Counted x Dilution x 1,0000)/ (Area counted x Depth)


Dilution: 20

Area of fluid: 4 ( as in WBC Count)

Depth of fluid: 10

= N x 50,000

Micro Loop Factor (MLF)

  • The radius of the spot smear (R) = 4 mm
  • The radius of the microscope objective (r) = 0.1 mm
  • Amount of the suspension in each spot = 5μl = 0.005ml
  • Total number of fields counted = 8
Micro Loop Factor Formula

MLF = 4×104

of AFBs count per ml =                


       AFBs count in 8 microscopic fields

Dilution Factor =

AFB count per ml

                                3.3 X 105

Note that the optimum dose of bacilli to inoculate mice with is 10,000 bacilli per mL.  Per food-pad is 10,000/0.003 = 3.3 x 105

Derived Test for Direct Bilirubin

Direct Bilitubin= Total Bilirubin (TBil)-Unconjugated bilirubin (Bu)

Delta Bilirubin Estimation

Delta Bilirubin(DELB)=Total bilurubin (TBill)- (Bu+Bc)
Where Bu stands for unconjugated bilirubin andBc for Conjugated bilirubin.


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