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Published on: February 15, 2011
Histoplasmosis relapse in patients with AIDS: detection using Histoplasma capsulatum variety capsulatum antigen
L J Wheat1, P Connolly-Stringfield, R Blair
1Department of Internal Medicine, Indiana University, Indianapolis 46202.
Objective:
To assess the accuracy of Histoplasma capsulatum variety capsulatum polysaccharide antigen testing for the identification of histoplasmosis relapse in patients with the acquired immunodeficiency syndrome (AIDS).
Design:
A retrospective study using stored specimens.
Setting:
A referral center and several private hospitals.
Patients:
Twenty episodes of histoplasmosis relapse were evaluated in 17 patients with AIDS from November 1987 to August 1990. Controls included 30 patients with AIDS and histoplasmosis who did not have a relapse during maintenance therapy and who were initially tested during the same week as the patients with relapse. A second control group included seven patients with AIDS and histoplasmosis who were evaluated for relapse on 23 occasions; relapse, however, was excluded on each occasion.
Measurements:
To avoid interassay variability, specimens were tested for H.c. var. capsulatum polysaccharide antigen with the same radioimmunoassay.
Main Outcome Measure:
The change in the H.c. var. capsulatum polysaccharide antigen level during successful as opposed to unsuccessful maintenance therapy for the prevention of histoplasmosis relapse.
Main Results:
For the 20 episodes of relapse (17 patients), H.c. var. capsulatum antigen levels increased by at least 2 radioimmunoassay units in 12 of 14 serum specimens tested (85.7%; 95% Cl, 57.2% to 98.2%) and in 17 of 18 urine specimens tested (94.4%; Cl, 72.7% to 99.9%). Antigen levels increased in the urine or serum in 1 of 83 specimens (1.2%; CI, 0.03% to 6.6%) obtained on 56 occasions (1.8%; CI, 0.04% to 9.6%) from controls (specificity, 98.2%; CI, 90.4% to 99.96%). In three cases of relapse, antigen levels increased before clinical relapse, antigen levels increased before clinical relapse was suspected. Complement fixation titers increased by at least 2 dilutions in 4 of 11 cases (36.4%; CI, 10.9% to 69.2%) but in 0 of 9 control patients (CI, 0% to 28.3%).
Conclusion:
An increase in H.c. var. capsulatum polysaccharide antigen levels of 2 units or more strongly suggests histoplasmosis relapse. The presence of increasing titers of anti-H.c. var. capsulatum antibodies by complement fixation is less accurate for the diagnosis of relapse.
Insights
An increase in Histoplasma capsulatum polysaccharide antigen levels strongly suggests histoplasmosis relapse in AIDS patients. This antigen test is more accurate than complement fixation titers for diagnosing relapse.
Area of Science:
- Mycology
- Infectious Diseases
- Immunology
Background:
- Histoplasmosis is a significant opportunistic infection in patients with acquired immunodeficiency syndrome (AIDS).
- Accurate identification of histoplasmosis relapse is crucial for effective patient management and preventing mortality.
- Current diagnostic methods for relapse may have limitations in sensitivity and specificity.
Purpose of the Study:
- To evaluate the diagnostic accuracy of Histoplasma capsulatum variety capsulatum polysaccharide antigen testing for identifying histoplasmosis relapse.
- To compare the utility of antigen testing with complement fixation titers in detecting relapse.
Main Methods:
- A retrospective study analyzing stored serum and urine specimens from patients with AIDS.
- Inclusion of 20 relapse episodes in 17 patients and control groups of patients without relapse.
- Standardized radioimmunoassay used for H.c. var. capsulatum polysaccharide antigen detection to ensure consistency.
Main Results:
- Elevated H.c. var. capsulatum antigen levels (≥2 units) were observed in 85.7% of serum and 94.4% of urine specimens during relapse.
- High specificity (98.2%) was achieved, with minimal antigen level increases in control groups.
- Antigen levels increased prior to clinical suspicion of relapse in three instances.
Conclusions:
- A ≥2 unit increase in H.c. var. capsulatum polysaccharide antigen levels is a strong indicator of histoplasmosis relapse in AIDS patients.
- Antigen testing demonstrates superior accuracy for diagnosing relapse compared to complement fixation antibody titers.
