HIV INFECTION AND ITS EFFECTS ON THE BODY: ASYMPTOMATIC PERIOD-KEEPING TRACK OF ASYMPTOMATIC HIV INFECTION
During the asymptomatic period, your physician will probably keep track of the progress of the infection by physical examinations and with two principal tests. One test is to count, at regular intervals, the number of CD4 cells in the blood. The normal count is between 700 and 1,300 CD4 cells per milliliter of blood (five milliliters is one teaspoon). The average person has a CD4 count of about 1,000. People’s CD4 counts vary for several reasons. One reason is that different laboratories, counting CD4 cells in the same person or the same blood sample on the same day, can get counts that differ by as much as 20 percent. Another reason is that the CD4 count naturally varies in any one person over time, for reasons that are independent of HIV infection but are poorly understood. Consequently, a CD4 count of 500 one time may be 400 or 600 the next time; this is considered a normal variation. Because of this normal variability in the counts, a test showing a dramatic change in the count might need to be repeated.
In a person with HIV infection, the CD4 count decreases, on average, by 85 to 100 cells per year. Most people do not develop symptoms until their CD4 counts are below 300, and the average CD4 count for a person with an AIDS-defining diagnosis is 50—100. At a decrease of about 100 CD4 cells a year, the person who starts with a count of about 1,000 will develop symptoms after five to eight years, and will develop AIDS two or three years after that. The CD4 counts in some people fall more rapidly, while the CD4 counts in other people stabilize for several years. The CD4 count is the best measure of the progress of the infection. Physicians also use the CD4 count to determine what sorts of treatment will be helpful and to determine the benefit of the treatments used.
A second method for keeping track of the infection is through blood counts. Blood counts are counts of the numbers of the different kinds of cells in the blood: red cells, white cells, and platelets. Red blood cells deliver oxygen to the rest of the body; without enough oxygen, the
person loses energy, is tired much of the time. A low count of red blood cells is called anemia. White blood cells (the CD4 cell is only one kind of white blood cell) are part of the immune system’s defense against certain types of infection. A low count of white blood cells is called leukopenia. Platelets are cells that are critical in the process of blood clotting; a low number of platelets may result in excessive bleeding. During the asymptomatic period, the blood counts, like the CD4 counts, may also fall. That means that the body has progressively fewer red blood cells, fewer white blood cells, and/or fewer platelets. The body, however, has a great reserve, a large overabundance, of all three kinds of blood cells. The blood count must be lowered severely before symptoms occur.
*41\191\2*
