Working of the Blood Cell Counter

Click on the site to see a nice animation of the Flow Cytometer. It is one of the automated ways to measure blood cells:


http://www.unsolvedmysteries.oregonstate.edu/flow_cytometry_06.shtml

You cane also read Page 351 of the textbook (Cromwell, Weibell and Pfeiffer) and refer to Fig. 13.4

Serological tests

Serological tests are any of several laboratory procedures carried out on a sample of blood serum, the clear liquid that separates from the blood when it is allowed to clot. The purpose of such a test is to detect serum antibodies or antibody-like substances that appear specifically in association with certain diseases.

Phlebotomy

Phlebotomy is the process of drawing blood samples by injecting a needle into a vein.


Patient Preparation

Patient is prepared according to test specific protocol. Good specimen quality ensures accurate results. Register tests as per the requisition slip. Seek clarification in doubt.


Fasting Requirements

A fasting morning specimen is preferred until specified otherwise. Results of tests whose sampling is done between 8.00 to 10.00 am are best interpreted with reference intervals.


Specimen Collection

Ensure patient's correct identity- Lab No., Name, Age, Sex, etc. Sampling done only after patient has rested for ten minutes. Refer to the Alphabetical List of Tests in Reference Guide for detailed instructions on specimen collection. Label & barcode the blood collection tubes prior to sampling. Select & prepare proper phlebotomy site. Puncture the vein when spirit has evaporated completely. Avoid sites of I/V infusion, hematoma, oedema & thrombosis. Do not apply tourniquet for more than one minute. Draw blood sample with minimum trauma using correct order of draw (Blood culture, SST/Red Top, Citrate, Heparin, EDTA, Flouride) and needle size (preferred 19-21G). Ensure correct volume draw for additive tubes. Mix the blood with the anticoagulant by gently inverting 8-10 times for additive tubes and 3-4 times for SST. Press the puncture site keeping the arm horizontal till blood stops flowing; apply Band - aid'.


Safety Precautions

Technicians/phlebotomists should wear gloves and apron for their safety. Destroy the needle in needle cutter after drawing blood. Discard sharps and other biological waste in proper bins containing disinfectant (1% sodium hypochlorite).

Beer Law Animation

Lambert Beer Law

Colorimeter

• Colorimeter is a device used for colorimetry. It measures the absorbance of different wavelengths of light in a solution. It is used to measure the concentration of a known solute.
  Different chemical substances absorb different wavelengths of light. When the concentration of the solute is more, it absorbs more light in a specific wavelength. This is known as Beer-Lambert law.
  
  


• Different parts
  The most important parts of a colorimeter are:
  a light source, which is usually an ordinary filament lamp
  an aperture which can be adjusted
  a set of filters in different colors
  a detector which measures the light which has passed through the solution
  
  


• Filters
  Different filters are used to select the wavelength of light which the solution absorbs the most. This makes the colorimeter more accurate. The usual wavelengths used are between 400 and 700 nanometers. If it is necessary to use ultraviolet light (below 400 nanometers) then the lamp and filters must be changed.
  
  


• Output
  The output of the colorimeter may be shown in graphs or tables, by an analogue or digital meter. The data may be printed on paper, or stored in a computer. It either shows the amount of light which is absorbed by the solution, or the amount of light which has passed through the solution.

How does a modern lab look like ?

A modern path. lab looks like the one mentioned above:

I have taken this from the Harvard Laboratory. The essential equipment in a clinical laboratory are :

1. Autoanalyser
2. Centrifuge
3. Bulbs
4. Refrigerator
5. Reagent Kits
6. Centrifuge tubes
7. Beaker and misc. glassware
8. Pippettes