Advances in Diagnosis and Treatment of Histoplasmosis

I am consulting on a patient with end-stage renal disease who recently underwent kidney transplantation. The patient developed a febrile illness, splenomegaly, respiratory distress and miliary pattern on chest x-ray. I suspect histoplasmosis, but the urine antigen was negative. Bronchoscopy was performed and Histoplasma was visualized in and cultured from lavage fluid. Are you aware of patients with severe histoplasmosis whose antigen test is negative?

Discussion

I have consulted on such patients. The antigen test was not performed at MiraVista. When urine was subsequently tested at MiraVista, it was highly positive, as was serum. Results may be falsely negative when testing is performed at laboratories other than MiraVista, as they use a different assay with different performance characteristics. To rule out false negative results, physicians at institutions that do not send Histoplasma antigen to our facility often send an additional specimen to MiraVista to test in the MVista® Blastomyces antigen assay which is entirely cross-reactive to Histoplasma antigen.

Histoplasmosis is usually asymptomatic or causes mild illness following acute exposure in healthy individuals but may be severe following intense exposure or in immunocompromised patients. Studies from the United States noted 3% mortality in patients with inflammatory disorders treated with biological agents [1], 5% in patients living with HIV/AIDS (PLHIV) [2] and 10% in solid organ transplant patients [3].

MiraVista Histoplasma Antigen Enzyme Immunoassay (MVista Ag EIA)

Results in patients with progressive disseminated histoplasmosis (PDH) are displayed in table 1 [4]. Antigen was detected in the urine in 90%: 92% in PLHIV, 94% with other immunocompromising conditions, 64% in those who are not immunocompromised, and 90% overall.

The MVista Ag EIA was used to assess response to treatment in patients with PDH in an AIDS Clinical Trial Group/Mycoses Study Group (ACTG/MSG) study [5-8]. The MVista Ag EIA was also used for diagnosing relapse [9].

The MVista Ag EIA is validated for testing multiple body fluids including urine [4, 10], serum [4, 10], bronchoalveolar lavage fluid (BAL) [11, 12] and cerebrospinal fluid (CSF) [13, 14] and complies with CLSI and New York requirements. It is also used for detection of antigen in other sterile body fluids.

Serum and urine testing provides the highest sensitivity for diagnosis. One hundred fifty-eight patients in whom both urine and serum were tested and at least one was positive found urine to be negative in 16% of patients in whom the serum was positive.

Monitoring antigen clearance is used as an aid in deciding when treatment can be discontinued. This is possible because results are highly reproducible, figure 1 [15]. Changes in serum concentration are more informative than urine. Serum concentration may be quantifiable when urine is above the limit of quantification, ALQ (20 ng/mL). If both are >20 ng/mL the urine may remain ALQ for a year or more while the serum declines into the quantifiable range within 1-2 months.

Commercial EIAs. Histoplasma antigen EIAs are also available from some commercial laboratories. Their performance characteristics differ from the MVD EIA, table 2.

MiraVista Histoplasma IgG and IgM Antibody EIA

The MVD Histoplasma antibody EIA is more sensitive (89%) than immunodiffusion (56%) or complement fixation (73%) [16]. Combined MiraVista IgG and IgM antibody and antigen detection in CSF was the most sensitive (98%) method for diagnosing Histoplasma meningitis and the specificity was 91%, table 3 [13].

Turnaround time (TAT). Another important feature of the MVD antigen and antibody EIAs is rapid TAT. Antigen testing is performed twice daily Tuesday through Friday and once daily Monday and Saturday and results are reported the day the specimen is received in 91%, within two days in 96%, and three days in 99%. Antibody testing is performed Monday and Wednesday through Saturday.

Recommendations for Diagnosis

  1. Combine Histoplasma antigen in urine and serum and IgG and IgM antibody testing in the serum to achieve highest sensitivity
  2. Bronchoalveolar lavage fluid should be tested if the urine and serum antigen are negative, and the illness is consistent with pulmonary histoplasmosis.
  3. Ship directly to MiraVista for most rapid turnaround time.

Monitoring Treatment. Monitor monthly during the first 3 months and then every 3-4 months during the first year of treatment. Continue treatment until antigen is no longer detected in the urine and serum [17]. Determine the antigen concentration at other times if there is concern about treatment failure or relapse.

 

Table 1. Diagnostic tests in progressive disseminated histoplasmosis.

Test PLHIV1
(N = 38)
OIC2
(N = 62)
NIC3
(N = 11)
ALL4
(N = 111)
Culture4 34/38 (89.5%) 57/61 (93.4%) 7/8 (87.5%) 98/107 (91.6%)
Pathology4 18/23 (78.3%) 32/38 (84.2%) 8/8 (100%) 56/68 (82.3%)
Antigen5 35/38 (92.1%) 58/62 (93.5%) 7/11 (63.6%) 100/111 (90.1%)

1Patients living with HIV, 2other immunocompromise, 3non-immunocompromise, 4proven, 5probable

 

Table 2. Comparison of MiraVista Histoplasma antigen EIA with other commercial tests.

Parameter MVD antigen EIA Commercial EIAs
Accurate quantification Yes Unknown
Reproducibility, figure 1 Excellent [15] Unknown
Monitoring treatment Yes [8] Unknown
Diagnosis relapse or treatment failure Yes [9] PLHIV Unknown
Sensitivity PDH 92% [4] to 100% [9] 92% [18]
Specificity PDH 99% [4, 15] 51% [18]
Specimens tested Urine, Serum, BALF, CSF, OBF** Unknown
Limit of detection 0.2 ng/mL Unknown
Non-quantifiable >20 ng/mL* Unknown
Turnaround time 1 day 91%, 2 days 96%, 3 days 99% Unknown
Expert clinical consultation Yes Unknown
Publications >50 <10
*serum usually quantifiable, **other body fluids

 

Table 3. Combined antigen and antibody detection for diagnosis of Histoplasma meningitis [13].

Test Sensitivity Specificity
Antigen 78% (39/50) 97% (140/145)
IgG or IgM antibody 82% (37/45) 93% (142/153)
Antigen or antibody 98% (48/49) 91% (139/153)
Culture 19% (9/47) 100% (119/119)

 

Figure 1 Reproducibility: urine tested in the same or different assays [15].
Reproducibility: urine tested in the same or different assays

 

Reference List

  1. Vergidis P, Avery RK, Wheat LJ, et al. Histoplasmosis Complicating Tumor Necrosis Factor-alpha Blocker Therapy: A Retrospective Analysis of 98 Cases. Clin Infect Dis 2015 Aug 1; 61(3):409-17.
  2. Myint T, Anderson AM, Sanchez A, et al. Histoplasmosis in Patients With Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome (HIV/AIDS): Multicenter Study of Outcomes and Factors Associated With Relapse. Medicine (Baltimore) 2014 Jan; 93(1):11-8.
  3. Assi M, Martin S, Wheat LJ, et al. Histoplasmosis after solid organ transplant. Clin Infect Dis 2013 Dec; 57(11):1542-9.
  4. Hage CA, Ribes JA, Wengenack NL, et al. A multicenter evaluation of tests for diagnosis of histoplasmosis. Clin Infect Dis 2011 Sep; 53(5):448-54.
  5. Wheat LJ, Connolly-Stringfield P, Blair R, et al. Effect of successful treatment with amphotericin B on Histoplasma capsulatum variety capsulatum polysaccharide antigen levels in patients with AIDS and histoplasmosis. Am J Med 1992 Feb; 92(2):153-60.
  6. Wheat LJ, Cloud G, Johnson PC, et al. Clearance of fungal burden during treatment of disseminated histoplasmosis with liposomal amphotericin B versus itraconazole. Antimicrob Agents Chemother 2001 Aug; 45(8):2354-7.
  7. Wheat LJ, Connolly P, Haddad N, Le Monte A, Brizendine E, Hafner R. Antigen clearance during treatment of disseminated histoplasmosis with itraconazole versus fluconazole in patients with AIDS. Antimicrob Agents Chemother 2002 Jan; 46(1):248-50.
  8. Hage CA, Kirsch EJ, Stump TE, et al. Histoplasma Antigen Clearance during Treatment of Histoplasmosis in Patients with AIDS Determined by a Quantitative Antigen Enzyme Immunoassay. Clin Vaccine Immunol 2011 Apr; 18(4):661-6.
  9. Wheat LJ, Connolly-Stringfield P, Blair R, Connolly K, Garringer T, Katz BP. Histoplasmosis relapse in patients with AIDS: detection using Histoplasma capsulatum variety capsulatum antigen levels. Ann Intern Med 1991 Dec 15; 115(12):936-41.
  10. Durkin M, Estok L, Hospenthal D, et al. Detection of coccidioides antigenemia following dissociation of immune complexes. Clin Vaccine Immunol 2009 Oct; 16(10):1453-6.
  11. Wheat LJ, Connolly-Stringfield P, Williams B, et al. Diagnosis of histoplasmosis in patients with the acquired immunodeficiency syndrome by detection of Histoplasma capsulatum polysaccharide antigen in bronchoalveolar lavage fluid. Am Rev Respir Dis 1992 Jun; 145(6):1421-4.
  12. Hage CA, Davis TE, Fuller D, et al. Diagnosis of Histoplasmosis by Antigen Detection in BAL Fluid. Chest 2010 Mar; 137(3):623-8.
  13. Bloch KC, Myint T, Raymond-Guillen L, et al. Improvement in Diagnosis of Histoplasma Meningitis by Combined Testing for Histoplasma Antigen and Immunoglobulin G and Immunoglobulin M Anti-Histoplasma Antibody in Cerebrospinal Fluid. Clin Infect Dis 2018 Jan 6; 66(1):89-94.
  14. Wheat J, Myint T, Guo Y, et al. Central nervous system histoplasmosis: Multicenter retrospective study on clinical features, diagnostic approach and outcome of treatment. Medicine (Baltimore) 2018 Mar; 97(13):e0245.
  15. Connolly PA, Durkin MM, LeMonte AM, Hackett EJ, Wheat LJ. Detection of Histoplasma antigen by a quantitative enzyme immunoassay. Clin Vaccine Immunol 2007 Dec; 14(12):1587-91.
  16. Richer SM, Smedema ML, Durkin MM, et al. Improved Diagnosis of Acute Pulmonary Histoplasmosis by Combining Antigen and Antibody Detection. Clin Infect Dis 2016 Apr 1; 62(7):896-902.
  17. Wheat LJ, Freifeld AG, Kleiman MB, et al. Clinical practice guidelines for the management of patients with histoplasmosis: 2007 update by the Infectious Diseases Society of America. Clin Infect Dis 2007 Oct 1; 45(7):807-25.
  18. Caceres DH, Gomez BL, Tobon AM, Chiller TM, Lindsley MD. Evaluation of OIDx Histoplasma Urinary Antigen EIA. Myco 2021 Nov 20.