The diagnostics and treatment of tropical diseases

by E. R. Stitt

Tests for Albumin.—The simplest and most reliable test for albumin is the heat test with the subsequent addition of a sufficient number of drops of 5% acetic acid to make the boiled urine acid and incidentally to dissolve any phosphates which may have separated out on boiling.

Ulrich’s test is a very simple one and only calls for reagents which are usually at hand. Heat a saturated solution of common salt, containing 2% of glacial acetic acid, and superimpose the urine to be tested upon the hot reagent. A ring shows the presence of albumin.

For Heller’s test, pour a small amount of nitric acid into a narrow test tube and, while holding the tube at an angle of about 45°, superimpose a layer of the urine to be tested, which is delivered drop by drop from a pipette and allowed to flow down the side of the tube.

This test can be converted into a quantitative one which is sufficiently accurate for clinical purposes. It is based on the fact that a specimen of urine containing 0.003% of albumin will give a perceptible ring at the layering of the urine and acid in two minutes. If the ring appears at once or in a few seconds the albumin content is greater. From the qualitative test an idea can be formed as to the amount of albumin which the urine contains, a heavy ring forming immediately showing a considerable albumin content. Probably the highest elimination of albumin is found in chronic parenchymatous nephritis where it may run from 1 to 3%. In an ordinary case of acute nephritis O.5% would be an average content.

Recently I have been using for both qualitative and quantitative albumin tests the following apparatus. This is simply a 5-inch piece of ¼-inch soft glass tubing heated at a point 2 inches from one end, drawn out for about 2 inches and bent to form a U-tube with one end shorter than the other. This form of tube enables one to perform two tests with the same column of nitric acid and is easily cleaned and dried. They may be kept suspended around a glass tumbler’s rim. Taking up a small amount of nitric acid with a capillary bulb pipette it is deposited in the capillary curve of the bent tube. This acid pipette should be kept attached to the acid bottle. With a second pipette the urine is deposited in the short arm of the U-tube and the presence of albumin shows by a distinct ring at the junction of urine and acid in the clear capillary tubing. The long arm will serve for the introduction of a second specimen of urine for the albumin test.

For quantitative test we dilute the filtered urine with one or more parts of normal salt solution according to the intensity of the albumin ring. A very convenient way of making the dilution is with a graduated centrifuge tube. Make a one to ten dilution of the urine, mix and draw up with a bulb pipette and deposit in the short arm of the U-tube. A distinct ring forms in two or three seconds. Pour off one-half of the diluted urine and make up with an equal amount of saline. Deposit this one to twenty dilution in the long arm. The ring forms in about a minute. With further testing it is found that a one to forty dilution shows a perceptible ring in just two minutes. This final and successful dilution multiplied by 0.0033 gives the percentage of albumin in the urine (40 × 0.0033 = 0.13%).

Should it be desired to determine the nature of the proteids present either in urine or in exudates or transudates the following method is applicable. Determine the percentage of total proteid by the method employed above. Then throw down the globulins by the addition of an equal amount of a saturated solution of ammonium sulphate, filter and estimate the proteid content of the filtrate. The difference between that and the total gives the percentage of globulin. The filtrate is now treated with 5% acetic acid until a precipitate of nucleo-proteid ceases to form; the fluid is filtered and the clear filtrate (which should not show any turbidity with a drop of 5% acetic acid) is tested for its proteid content, which represents the serum albumin. When the combined percentage of globulins and serum albumin is subtracted from the total proteid percentage we have the percentage of nucleo-proteid.

Tests for Blood.—Very important in tests of the urine are those for blood. With an unaided eye a smoky colored urine, more or less reddish-brown in color, is suggestive in cases of haematuria, while in haemoglobinuria we usually have a more or less porter-colored, turbid fluid which, however, shows a clear haemoglobin-tinged fluid when centrifuged to throw down the haemoglobin casts and granular débris of the disintegrated red cells. Upon shaking such urine we get a pinkish foam instead of the yellowish one of icteric urine.

A strip of white filter-paper when partially dipped into urine shows pinkish-colored waves which are more deeply colored at the summit of the waves while the paper which absorbs bile-containing urine shows the yellowish color and waves less yellow at the summits of the colored waves.

For haematuria we may use either the microscopic method for the recognition of red cells or chemical ones. The red cell is best recognized by the double contour of the 7.5 micron disk. Spores of moulds, which greatly resemble red cells, are smaller, usually not more than 5 microns.