Quality of Reagents and Solutions - labsstudies

Quality of Reagents and Solutions

Quality of Reagents and Solutions

Quality of Reagents and Solutions

The quality of reagents and solutions is the most important factor in achieving good testing results, accuracy, and precision in patient samples.

Before performing the laboratory tests that need reagents and solutions they should be first checked for quality.

Quality Testing Measures

  •  Examine the solution’s condition in relation to expectations: volume, color, and clarity.
  •  As a quality control measure, patient whole blood samples with known results are frequently used.  As an example, Using the previous batch of Drabkin’s and newly prepared Drabkin’s, test the patient’s whole blood for known haemoglobin. Test the patient’s whole blood with a previous batch of Turk’s reagent and a newly prepared batch of Turk’s reagent to compare the results.
  • Blood smear slides from patients with known parasites are used as quality control. For example, stain the patient blood film with known malaria parasites and compare the results using the previous batch of Field and Giemsa stain and the new batch of Field and Giemsa stain.

 

Quality of Common Reagents and solutions

The following are common reagents and solution’s, as well as methods for ensuring their quality:

1. Drabkin’s solution:

  •  Follow the expiry date.
  • Take note that the solution is clear and yellow. This is supported by spectrophotometric evidence.
  • Set the spectrophotometer to 540 nm and allow it to warm up per SOP.
  • In a clean cuvette, place 5.0 mL of freshly prepared reagent to blank the colorimeter.
  • Pipette 20 L of well-mixed blood with a known haemoglobin concentration into a test tube containing 5.0 mL reagent, mix thoroughly, and pour into a clean dry cuvette.
  •  Determine the absorbance at 540 nm (wavelength).
  • Determine the haemoglobin result based on the calibration curve (table of values).
  •  The result should agree within + 0.5 g/dL of the previous result to verify the quality of freshly prepared reagent.

 

2. Turk’s Reagent:

  •  Take note that the freshly prepared reagent is purple and clear when compared to the previous batch.
  •  Pipette 20 L of mixed whole blood into a labeled test tube containing 380 L fresh Turk’s reagent according to SOP.
  •  Pipette 20 L of mixed whole blood into a second labeled test tube containing 380 L of the previous batch Turk’s reagent.
  •  Tap both tubes together and set aside for at least one minute.
  •  Using SOP, fill one Neubauer counting chamber with the fresh batch of Turks and the other chamber with the previous batch of Turks.
  •  After 2 minutes, look for the absence of red blood cells in both chambers.
  • Compare results to ensure that white blood cells are easily visible in both chambers according to SOP.

 

3. Field stains:

  •  Prepare two thin blood films from a confirmed P falciparum patient.
  •  Stain according to SOP with the previous batch and the new batch of Fields stain.
  • Examine the staining results.
  •  If the staining of the fresh stain is poor, allow it to “mature” for 3-7 days before using it on patient testing.
  • Check the staining quality of the P falciparum thin blood film again.
  • If the staining remains poor, discard it and start over.

 

4.  Giemsa:

  •  Prepare two thin blood films from a patient with confirmed P falciparum infection.
  •  Stain with the previous batch and the new batch of stain according to SOP.
  • Compare the staining results.
  •  If the staining of the fresh stain is poor, discard it and start over. This attribute
  • The reagent should be tested every 2-3 weeks.

 

5. Acridine orange:

  •  Prepare two thin blood films from a patient with confirmed P falciparum infection.
  •  Stain with the previous batch and the new batch of stain according to SOP.
  • Using a fluorescent microscope, and compare the staining results.
  • This microscope can only be used to check quality in hospitals.
  • If the staining of the fresh stain is poor, discard it and start over.

 

6.  0.85% W/V physiological saline:

  •  Note that the solution is clear and colorless.

 

7.  0.25% Iodine:

  •  For two microscope slides, prepare a fresh stool sample containing parasite eggs or cysts.
  • Stain one with previously prepared iodine stain and one with a new batch of iodine stain according to the SOP.
  •  Compare parasite cyst and egg staining results.

 

8.  1% Eosin stain:

  • Prepare two microscope slides with fresh stool sample containing parasite trophozoites.
  • Stain one with previously prepared eosin stain and one with a new batch of stain according to the SOP.
  • When observing parasite trophozoite staining, compare the results.

 

9. ZN stain:

  •  Prepared two slides of positive AFB sputum smears.
  •  Test one slide with the new Carbol Fuchsin stain batch and the other with the old stock stain.
  •  Contrast the staining reactions.
  • If the new stain produces poor staining, discard it and make new reagents.

 

10. Distilled water:

  •  Note that the solution is clear and colorless.

 

11. Filtered rain water:

  •  Use Whatman filter paper.
  • Note that the solution is clear and colorless.

Read also: Preparation of Solution for Ziehl Neelsen stain

Important Point

The general types of tests for the quality of recently prepared reagents involved examining the color and clarity of the newly prepared reagent and comparing it to the previous batch.

In addition, known positive samples are tested with the previous batch of reagent and a newly prepared batch of reagent, and the results are compared.

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