Correlation of Clinical Outcomes with -Glucan Levels in Patients with Invasive Candidiasis Charles R. Sims,a Siraya Jaijakul,a John Mohr,b Jose Rodriguez,a Malcolm Finkelman,c and Luis Ostrosky-Zeichnera Laboratory of Mycology Research, Division of Infectious Diseases, University of Texas Health Science Center at Houston, Houston, Texas, USAa; Cubist Pharmaceuticals, Lexington, Massachusetts, USAb; and Associates of Cape Cod, Falmouth, Massachusetts, USAc
The correlation of -glucan (BG) levels with clinical outcomes in invasive candidiasis (IC) remains unknown. Patients with proven IC were followed prospectively from diagnosis to outcome with twice-weekly serum BG sampling. Correlation of BG with clinical outcome was assessed in each patient. BG levels tend to decrease in successfully treated patients and increase in treatment failures. BG levels may be useful as surrogates for outcome evaluation of IC.
C
urrent diagnostic methods for invasive candidiasis (IC) are disappointing (8). Blood cultures are positive in only 50% of patients with candidiasis, and the attributable mortality rate of patients with candidemia approaches 40% (9). The limited sensitivity of serial blood cultures as a marker for clinical response in a disease with a high mortality is troublesome. -Glucan (BG) is a fungal cell wall component that can be detected in serum. Current diagnostic kits have shown high sensitivity and specificity for the diagnosis of a wide variety of fungal infections, including candidemia (3). While BG has excellent diagnostic performance (6), there are limited data that correlate BG levels with a clinical or microbiological outcome (2, 4). Establishing whether or not such a relationship exists might allow BG to be used as a surrogate marker for response to therapy and prognosis in clinical practice. (This study was partially presented at the 46th Interscience Conference on Antimicrobial Agents and Chemotherapy, San Francisco, CA, 27 to 30 September 2006.) This is a single-center, prospective observational study. All adult patients with blood cultures positive for Candida spp. and who met the European Organization for Research and Treatment of Cancer Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) criteria for proven fungal infections (1) were eligible for the study. Informed consent was obtained, and patients were enrolled within 96 h of a positive culture and 24 h of initiation of any systemic antifungal therapy. This project was reviewed and approved by the institutional committee for the protection of human subjects. A 5-ml serum specimen was collected at baseline and twice weekly from each patient being treated for IC. Blood samples were obtained through either central venous catheter (CVC) or peripheral venipuncture. Basic clinical data were collected, and patients were observed by the study team for evidence of clinical response or disease progression. The clinical response was assessed at the end of therapy and categorized as (i) success, significant or complete resolution of signs and symptoms of the Candida infection and no additional systemic antifungal treatment required, or (ii) failure, no significant improvement in signs and symptoms or death due to Candida infection. Serum was frozen at ⫺80°C until completion of enrollment. The samples were then analyzed using the commercially available Fungitell
TABLE 1 Demographic characteristics, Candida species isolated, and sites of infection of 67 patients
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Characteristics
No. (%) of patients
Risk factors Antibiotics Central venous catheter Any surgical procedure Abdominal surgery ICU care Use of total parenteral nutrition Use of steroids Immunosuppressives Hemodialysis Active malignancy
66 (99) 66 (99) 46 (69) 24 (36) 35 (52) 36 (54) 24 (36) 6 (9) 21 (31) 2 (3)
Candida species C. albicans C. glabrata C. parapsilosis C. tropicalis C. krusei C. guilliermondii Polymicrobial infections
24 (36) 16 (24) 16 (24) 6 (9) 1 (1) 1 (1) 3 (5)
Sites of infectiona CVC-related candidemia Peritonitis Endocarditis Osteomyelitis Other sources
55 (82) 10 (15) 4 (6) 1 (1) 4 (6)
a
Total is ⬎100% due to mixed infections.
kit (Associates of Cape Cod, Inc.). A BG level of ⬎60 pg/ml is considered positive with this kit. Serologic outcomes were assessed independently from clinical outcomes by evaluating BG levels using two different methods.
Received 22 March 2012 Accepted 23 March 2012 Published ahead of print 29 March 2012 Address correspondence to Siraya Jaijakul,
[email protected]. Copyright © 2012, American Society for Microbiology. All Rights Reserved. doi:10.1128/JCM.00773-12
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-Glucan in Invasive Candidiasis
FIG 1 Initial and final -glucan levels in successfully treated patients (n ⫽ 60) and in treatment failures (n ⫽ 7).
First, the initial and final BG values were compared, and success was considered a reduction in BG by ⬎5%. In the second method, BG levels were plotted over time, and Microsoft Excel software was used to calculate a best linear fit. The serologic outcome was considered successful if the slope of this best-fit curve was negative. Effects of antifungal medication and CVC removal on BG trends were compared using bivariate analysis with t test and Fisher’s exact test. A P value of ⬍0.05 was considered significant. Sixty-seven patients were enrolled. The mean age of those enrolled was 46 years (range, 17 to 85 years). Male patients (n ⫽ 42) made up 63% of those enrolled, and the mean ⫾ standard deviation (SD) length of follow-up was 17.5 ⫾ 11.9 days. Table 1 contains a list of patient risk factors, the species of Candida isolated from blood cultures, and the infection sites. The initial and final BG levels for patients with clinical success and for patients with clinical failure are shown in Fig. 1. For patients with clinical success (n ⫽ 60), the mean ⫾ SD initial and final BG levels were 399 ⫾ 545 pg/ml and 329 ⫾ 509 pg/ml (P ⫽ 0.0998); for patients with failure, the initial and final levels were 448.7 ⫾ 413.7 pg/ml and 946.9 ⫾ 1068 pg/ml (P ⫽ 0.1249), respectively. Agreements between clinical classification and serologic classification by methods 1 and 2 were 55% and 60%, respectively. BG level trends during treatment with different antifungal classes were examined. Patients who received amphotericin B had rising BG levels compared to those who did not receive polyenes antifungal therapy (odds ratio, 2.40; 95% confidence interval [CI], 1.46 to 3.97; P ⫽ 0.0048). Of those 10 patients who received amphotericin B and had a positive BG trend, nine patients had clinical success at the end of treatment. BG trends in patients who received fluconazole or echinocandin were not different from patients who did not receive these medications (P ⫽ 0.71 for fluconazole group and P ⫽ 0.61 for echinocandin group). Ninety-nine percent of patients (66/67) with candidemia had CVC at the time of diagnosis. Fifty-five out of 66 patients were diagnosed with CVC-related infection, and 54 patients had CVC removal. The mean ⫾ SD initial BG levels in patients with and without CVC-related infection were 349.04 ⫾ 468.72 pg/ml and 654.5 ⫾ 724.07 pg/ml (P ⫽ 0.07). In patients with CVC-related infection, BG trends were not statistically significantly different between patients with CVC removal and without CVC removal (P ⫽ 0.42). Although there is no significant change, BG levels tend to de-
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crease in successfully treated patients and increase in treatment failures. The trend in serial BG values is more consistent with clinical outcomes than using changes of absolute value of a single BG level since there are substantial differences in values between patients with similar diagnoses and outcomes. It is possible that different classes of antifungal agents may affect BG levels due to their mechanisms of action. Azoles are fungistatic, whereas polyenes and echinocandins are fungicidal. Theoretically, the polyenes and echinocandins may be associated with a measured “burst” of detectable BG in the serum after initiating these drugs. In our study, nine of 10 patients who received polyenes had positive BG trends despite clinical success. The rise of BG may be due to amphotericin B influence. However, there is no similar result observed in the echinocandins group. We should, however, caution the reader that our sample size is probably too small to make conclusions on this issue. Nett at al. showed that BG may be useful as a diagnostic tool of Candida biofilm and device-associated infections in an animal model (5). The rat models with device-associated infection had higher BG levels than those with invasive candidiasis without CVC (5). In our study, conversely, we found that patients with CVC-related candidemia had lower initial BG levels than patients with other invasive candidiasis. Intravenous catheter removal is recommended for treatment of patients with candidemia (7). Theoretically, BG trend should decrease after CVC removal. However, we found that there was no significant BG decrease observed in patients with CVC-related infection after removed catheters compared to those without CVC removal. In conclusion, the utility of BG as a prognostic marker for invasive candidiasis remains elusive, but there is a trend of kinetics of BG correlating with clinical outcome. Our study shows that the slope of BG showed better correlation to clinical outcome than using the percentage of reduction of initial and final levels of BG. There are limitations in our study, including the number of participants and correlation with microbiological results, and as an observational study, investigators lacked control over the use of antifungal agents or sites of blood drawn, which may affect the measured levels of BG. Further prospective experimental studies, including a larger number of patients, are warranted in order to confirm these preliminary findings. ACKNOWLEDGMENTS This work was supported by a research grant from Associates of Cape Cod. C.R.S., S.J., J.M., and J.R. have no transparency declarations to report. M.F. is an employee of Associates of Cape Cod, and L.O.-Z. has received research grants from Associates of Cape Cod.
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