CD4 Counts Higher in the Afternoon


Dr Conway Sorry to contradict you, but on December 3 you responded to a question about CD4 counts that they are higher in the morning and lower in the evening. According to all the studies I have seen this is not true and another doctor on this site confirms that CD4 counts are higher in the evening. It is important to correct this because you may not be the only doctor who gets this wrong and it could lead to some serious mistakes. You said that you always recheck CD4 counts if the percentage has not changed. Do you do this right away or do you wait three months for the next quarterly lab test?

The fact that the daily variation in CD4 counts is not always considered may lead to mistakes in making choices about therapy.

Also, shouldn't studies report when on average samples were taken? A difference of 200 from morning to night, which is normal could really throw off results, and comparisons between studies. For example,a 500 in the morning is much better than a 500 at night and may indicate a different state of health.


This is a fascinating point. In:

Stein DS, Korvick JA, Vermund SH. CD4+ lymphocyte cell enumeration for prediction of clinical course of human immunodeficiency virus disease: A review. J Infect Dis. 1992;165:352-63.

It suggests that CD4 counts are higher in the morning. However in:

Malone JL, Simms TE, Gray GC, Wagner KF, Burge JR, Burke DS.ources of variability in repeated T-helper lymphocyte counts from human immunodeficiency virus type 1-infected patients: total lymphocyte count fluctuations and diurnal cycle are important. J Acquir Immune Defic Syndr. 1990;3(2):144-51.

the opposite is suggested, with the limitation that the variations were small (60 cells or less).

However, all agree that the CD4 cell percentage is a more stable value and this is what you should look at if there is a significant cahnge in CD4 count between two measures in an individual and they were taken at different times of day. If the perecentage is stable, dirunal or other variations explains the difference between the two measures and this is of no concern. I would not even be inclined to repeat th CD4 count outside of what would be requested for routine care. However, if both the CD4 count and percentage are changing, I would repeat the CD4 count immediately to making sure this is not a worrisome trend.