NESTROFT test is used in the screening of

*NESTROF stands for naked eye single tube red cell osmotic fragility test. *Used in population screening for beta thalassemia trait (BTT).*Method: A stock solution of 10% buffered saline (pH 7.4) is prepared and dissolved in 1 litre of distilled water. 0.36% buffered saline is prepared by diluting 36 mL of 1 % buffered saline with 64 mL distilled water to make 100 mL.2mL of 0.36% buffered saline is taken in one tube (10 cm x 1 cm diameter) and 2 mL distilled water is taken in another. A drop of blood is added to each of the tubes, which are left undisturbed for half an hour at room temperature.After half an hour the contents of both the tubes are shaken and the tubes held against a white paper on which a thin black line is drawn. The line is clearly visible through the contents of the tube containing distilled water due to complete lysis. If the line is visible through the contents of the tube with buffered saline, the test is negative, whereas if the line is not visible, the test is positive.*Interpretation: A positive NESTROFT indicates that all red cells in the tested sample have not undergone lysis in 0.36% buffered saline. These unlysed red cells result in the hazy appearance of the contents of the tube and render the line on the paper indistinct. These red cells also sediment as a button at the bottom of the tube when it is left undisturbed for some time. Thus a positive NESTROFT indicates decreased red cell osmotic fragility and increased resistance to osmotic lysis.*Positive NESTROF test:b- thalassemia traitIron deficiency anemia (IDA)Liver diseasesHemoglobinopathies(Ref: Recent Advances in Hematology -3, 1/e p173)