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

234 Manual of basic techniques for a health laboratoryUrine specimens from infantsUrine can be collected into a plastic bag with an adhesive mouth. The bag is fixedaround the genitalia and left in place for 1–3 hours, depending on the examinationrequested. Colostomy bags can be used.7.1.2 Preservation of urine specimens●●Urine passed at a clinic and examined immediately does not requirepreservation.If urine has been collected to check for the presence of Schistosoma haematobiumova but it may not be examined for several hours, it should be acidified with afew drops of 10% acetic acid (reagent no. 2).7.2 Examination of urine specimens7.2.1 Appearance● Urine is normally clear straw-yellow in colour. More concentrated urine mayappear dark yellow.● The presence of blood cells or excess salts may make the urine appear cloudy.● Pigments from bile substances may make the urine appear deep yellow or brown.● Urine can occasionally appear colourless.Report the appearance as:— clear or cloudy;— colourless, pale yellow, deep yellow or brown.7.2.2 Testing for the presence of bloodElevated erythrocyte counts and haemoglobin levels may occur in urine:— after heavy physical exercise;— in vaginal tract infections;— in parasitic infections (e.g. schistosomiasis);— in acute glomerulonephritis;— in acute cystitis or urethritis;— in patients suffering from certain tumours.Blood cells are easily seen by microscopic examination after centrifugation (seesection 7.2.7).Lysed erythrocytes can be detected using a urine dipstick which has a segment fordetection of blood. Urine dipsticks are available for detection of a single substance(e.g. blood, glucose or protein) or for detection of several substances (e.g. nitriteand leukocyte esterase).MethodThe dipsticks are placed into the urine and immediately removed. They are thencompared with a comparison chart after an appropriate time that is also specifiedon the chart.The colour changes observed on the dipstick will give a semi-quantitative estimationof the amount of substance present. This can be reported as negative, +, ++,+++, ++++ or as an approximate value of the concentration of the substance testedfor.Dipsticks must be stored according to the manufacturer’s instructions.