Manual of basic techniques for a health laboratory - libdoc.who.int

7. Examination of urine 239The analytical range of this modified method is 25–700mg/l.Protein in urine can also be detected using a protein dipstick (see section 7.2.2).7.2.6 Detection of ketone bodiesNormal urine does not contain ketone bodies. Acetone and other ketone bodiesmay appear in urine:— in severe or untreated diabetes;— in certain other conditions (dehydration, vomiting, malnutrition, prolongedstarvation and following strenuous exercise).PrincipleWhen sodium nitroprusside (sodium nitrosyl pentacyanoferrate (III)) is added tourine containing ketone bodies, a purple colour is produced.Materials and reagents●●●●●●●Test-tubesTest-tube rackMeasuring cylinder, 10mlDropping pipetteSodium nitroprusside crystalsAcetic acidAmmonia.Method1. Just before carrying out the test, place a sufficient number of sodium nitroprussidecrystals into a test-tube to cover the bottom (Fig. 7.6).2. Add 5ml of distilled water. Shake well until the crystals are almost dissolved.(Not all the crystals are expected to dissolve as the solution is saturated.)3. Measure 10ml of urine into another test-tube.4. Add four drops of acetic acid to the urine, followed by 10 drops of freshly preparedsodium nitroprusside solution. Mix well.5. Holding the tip of the pipette against the side of the tube, let 20 drops (1ml) ofammonia solution flow on to the surface of the liquid (Fig. 7.7). Wait for 5 minutesbefore reading — a positive result may be obvious before this time.Fig. 7.6 Preparation of sodium nitroprusside solutionFig. 7.7 Adding ammonia solution to thesurface of the sodium nitroprussidesolution