Grill, Francisca J.

The diagnosis of coccidioidomycosis is often achieved serologically by the detection of antibodies against fungal antigens. While several serologic tests are available for coccidioidomycosis, all of them are performed in a laboratory setting causing delays in diagnosis and therapeutic intervention. Point-of-care testing offers the ability to provide a shorter time to result by avoiding specimen send-out, minimizing processing steps, and employing expeditious immunochemical techniques. A preliminary trial of a rapid anti-coccidioidal antibody lateral flow assay (LFA) using fingerstick blood was performed on 22 patients with coccidioidomycosis at the point of care during outpatient clinic visits. Patients were tested longitudinally over the course of one year. An LFA reader was implemented to provide an objective result by quantifying the intensity of the test line band. There was close qualitative concordance observed between positive LFA results with send-out immunodiffusion (89.5%) and complement fixation (78.4%) standard of care clinical laboratory assays. Additionally, the relationship between LFA test line density values and traditional complement fixation antibody titers was assessed.

Abstract Description Coccidiomycosis is an endemic fungal infection caused by Coccidioides spp., and diagnosis is often made with serology. Coccidiomycosis is especially problematic for immunocompromised patients, with greater risk for disseminated infection and mortality. This study evaluated current strategies for detecting antibodies to Coccidioides, including enzyme immunoassay (EIA), immunodiffusion (ID) and complement fixation (CF) and applied a new ID assay for improved sensitivity and specificity. Clinical sensitivity and specificity studies were done using 1544 unique serum specimens for which Coccidioides EIA testing was clinically requested. A full panel of EIA IgG, EIA IgM, ID and CF was performed on each, comparing our in-house immunodiffusion assay using reagents from Cactus Bio, LLC to our current reference laboratory. Full method validation was completed, as prescribed by CLIA. Using existing reference lab testing as the standard, a sensitivity of 96.9%, specificity 85.9%, PPV 54.9%, NPV 99.4% was achieved. Additional chart review demonstrated the in-house ID improved to 98.0% sensitivity, 94.6 specificity, 84.2% PPV, 99.4% NPV. Such high NPV supports using reflex testing, which allowed our lab to eliminate hundreds of unnecessary CF referrals each month, saving diagnostic time, financial waste and lab resources. A reflexive testing algorithm paired with this enhanced ID assay is especially useful for the immunosuppressed, for which Coccidioides infections carry a greater risk. Topic Categories Translational and Interventional Immunology (TI)

Abstract OBJECTIVE To compare 2 point-of-care lateral flow assays (LFAs) with immunodiffusion (ID) IgG results for anti-coccidioidal antibody detection in dogs with coccidioidomycosis. A further aim was to compare the quantifiable output of 1 of the LFAs to ID antibody titers. SAMPLE Serum banked from 73 client-owned dogs diagnosed with pulmonary or disseminated coccidioidomycosis. METHODS ID was used to determine antibody presence and titer against a coccidioidal antigen preparation. All sera were subsequently tested on an LFA based on recombinant chitinase 1 (CTS1) and the commercially available sōna LFA. LFA results were analyzed and compared to ID IgG results and clinical diagnosis. RESULTS All assays showed similar sensitivities in detecting anti-coccidioidal antibodies (83.6% to 89.0%). When compared with ID IgG, the CTS1 LFA had a positive percent agreement of 100%, while the sōna LFA had a positive percent agreement of 91.4%. Since the CTS1 LFA is semiquantitative, we were able to compare test line densities with ID titers and found a strong correlation between the 2 assays (Spearman ρ = 0.82). CLINICAL RELEVANCE This is the first side-by-side evaluation of a commercially available LFA (sōna) and a newer more rapid anti-CTS1 antibody LFA using serum from dogs with coccidioidomycosis. Both LFAs tested have similar sensitivity to ID IgG results. The CTS1 LFA can be read after 10 minutes and is semiquantitative, while the sōna LFA is read after 30 minutes, and the results are subject to interpretation. Accurate and fast detection of anti-coccidioidal antibodies allows clinicians to initiate appropriate treatment without diagnostic delay.

ABSTRACTCoccidioidesspp. are dimorphic fungi that are capable of infecting human and non-human mammals and can cause diverse manifestations of coccidioidomycosis or Valley fever (VF). In combination with clinical symptoms and radiographic findings, antibody-based diagnostic tests are often used to diagnose and monitor patients with VF. Chitinase 1 (CTS1) has previously been identified as the seroreactive antigen used in these diagnostic assays to detect anticoccidial IgG. Here, an indirect enzyme-linked immunosorbent assay to detect IgG to CTS1 demonstrated 165 of 178 (92.7%) patients with a positive result by immunodiffusion (ID) and/or complement fixation (CF) had antibodies to the single antigen CTS1. We then developed a rapid antibody lateral flow assay (LFA) to detect anti-CTS1 antibodies. Out of 143 samples tested, the LFA showed 92.9% positive percent agreement [95% confidence interval (CI), 84.3%–96.9%] and 97.7% negative percent agreement (95% CI, 87.9%–99.6%) with ID and CF assays. Serum or plasma from canines, macaques, and dolphins was also tested by the CTS1 LFA. Test line densities of the CTS1 LFA correlated in a linear manner with the reported CF and ID titers for human and non-human samples, respectively. This 10-min point-of-care test for the rapid detection of anti-coccidioidal antibodies could help to inform healthcare providers in real-time, potentially improving the efficiency of healthcare delivery.

In southwestern and western regions of the United States, at least half a million diagnostic tests for coccidioidomycosis (valley fever) are run annually. Enzyme immunoassays (EIAs) are blood tests which require precise dilution of patient serum prior to testing.

Abstract Background Coccidioidomycosis is often diagnosed with a collection of tests that measure a patient’s ability to mount an immune response to the fungus (antibody-based diagnostics) utilizing fungal protein preparations. Here we present an antigen-based assay that detects and quantifies coccidioidal chitinase-1 (CTS1) in diagnostic antigen preparations with potential for use in human serum. Methods An inhibition-based enzyme-linked immunoassay (ELISA) was developed that utilizes a monoclonal antibody specific for coccidioidal CTS1. CTS1 was quantified in commercial antigen preparations using recombinant CTS1 as a standard. Sera from 192 individuals from an endemic area were tested which included 78 patients (40.6%) with proven or probable coccidioidomycosis. Results The quantity of CTS1 in diagnostic commercial antigen preparations from different suppliers varied. Temporal constraints of availability of different lots of commercial antigens does not allow for immediate comparison of lot-to-lot variability. Assay results from patient serum samples correlated with low- and high-titer serology from patients with a coccidioidomycosis diagnosis. Further analysis suggested that patient derived anti-CTS1 antibodies may overlap with the mouse monoclonal antibody used in the assay. This unexpected overlap in CTS1 binding suggests the assay can detect antigen, antibody, or both, which contributes to its high level of clinical sensitivity of 89.74% and specificity of 94.90%. Conclusions The CTS1 inhibition ELISA described in this report is a promising tool to aid in quality control of antigens used in the diagnosis of coccidioidomycosis. Further optimization is needed to harness its utility as a diagnostic tool to aid in diagnosis and disease monitoring of coccidioidomycosis.