Lymphocytopenia in a hospital population--what does it signify?

Lymphocytopenia is a common finding in hospital patients especially since the advent of automated differential leukocyte counters. The causes and significance of lymphocytopenia are generally poorly understood. There has been no large-scale study of its significance for 25 years. The HIV epidemic, and the recently described idiopathic CD4+ T-lymphocytopenia have raised interest in this finding.

To describe the spectrum of lymphocytopenia in an adult teaching hospital and investigate its clinical significance.

Using the available computer facilities, patients with significant lymphocytopenia (< 0.6 x 10(9)/L) were identified over a 102 day period and diagnoses, operations and medication lists obtained. Where necessary, patient histories were examined to supplement the above information. If feasible, previous and subsequent lymphocyte counts were checked to establish if the lymphocytopenia were temporary or longstanding.

One thousand and forty-two patients were identified, with a mean age of 59.6 years, of whom 563 were male, and 757 were inpatients. Thirty-six patients were pancytopenic. We checked previous and subsequent counts for 698 patients and found 45 patients who were consistently lymphocytopenic, some for more than ten years. Thirty-four patients with previously normal counts remained lymphocytopenic throughout follow up, while 457 had at least one subsequent lymphocyte count > 1 x 10(9)/L. We found only one patient who was suspected of having idiopathic CD4+ T-lymphocytopenia. Patients fell into several categories (with some overlap): bacterial/fungal sepsis (250), post-operative (228), corticosteroid therapy (definite 159, suspected 53, inhaled steroids alone 14), malignancy (174 definite, six probable), cytotoxic therapy and/or radiotherapy (90), trauma or haemorrhage (86), transplants (73-38 renal and 35 bone marrow), 'viral infections' (26) and HIV infection (13). Thirty-four patients died within the study period.

Lymphocytopenia in hospital patients is most frequently reversible, and due to acute illness, notably sepsis and trauma (including surgery). Malignancy, with or without chemotherapy, and steroid use are also common causes, but HIV infection is a relatively uncommon cause in our hospital.