Measurement of a Novel Biomarker, Secretory Phospholipase A2 Group IIA as a Marker of Sepsis: A Pilot Study.

INTRODUCTION: Early identification of sepsis is critical as early treatment improves outcomes. We sought to identify threshold values of secretory phospholipase A2 (sPLA2)-IIA that predict sepsis and bacterial infection compared to nonseptic controls in an emergency department (ED) population. MATERIALS AND METHODS: This is a prospective cohort of consenting adult patients who met two or more systemic inflammatory response syndrome (SIRS) criteria with clinical diagnosis of infectious source likely (septic patients). Controls were nonseptic consenting adults undergoing blood draw for other ED indications. Both groups had blood drawn, blind-coded, and sent to an outside laboratory for quantitative analysis of sPLA2-IIA levels. The study investigators reviewed patients' inpatient medical record for laboratory, imaging, and microbiology results, as well as clinical course. RESULTS: sPLA2-IIA levels were significantly lower in control patients as compared to septic patients (median = 0 ng/ml [interquartile range (IQR): 0-6.5] versus median = 123 ng/ml [IQR 44-507.75]; P < 0.0001). SPLA2-IIA levels were higher in patients with confirmed source (n = 28 patients, median = 186 ng/ml, 95% confidence interval = 115.1-516.8) as compared to those with no source identified or a viral source (n = 17, median = 68 ng/ml, 95% confidence interval = 38.1-122.7; P = 0.04). Using a cutoff value of 25 ng/ml, sPLA2-IIA had a sensitivity of 86.7% (confidence interval 72.5-94.5) and a specificity of 91.1% (confidence interval 77.9-97.1) in detecting sepsis. CONCLUSIONS: sPLA2-IIA shows potential as a biomarker distinguishing sepsis from other disease entities. Further study is warranted to identify predictive value of trends in sPLA-IIA during disease course in septic patients.

Distinguishing septic from normal donors by detection of sPLA2-IIA from human plasma using a microsieve-based immunoassay.

Bloodstream infections that progress to septic shock are responsible for hundreds of thousands of deaths each year, and are associated with significant healthcare costs. Recent studies have shown that a member of the secreted phospholipase protein family, termed sPLA2-IIA, may play a role during the innate immune response to bacterial infections, and is elevated in the plasma of septic patients. In this report, the feasibility of a simple microsieve-based sPLA2-IIA detection immunoassay was explored. Microsieves containing 5µm pores were covalently coupled with a sPLA2-IIA-specific monoclonal antibody at 0.1, 1.0, and 10µg/mL and then assayed with plasma-based positive and negative controls to determine the optimal coating concentration. Recombinant sPLA2-IIA was then serially diluted to a final concentration of 200, 100, 50, 25, 12.5, and 6.25ng/mL and tested alongside a non-spiked sample to estimate the detection limit of the prototype assay. Recombinant sPLA2-IIA was also spiked into serum, EDTA-plasma, and Lithium-Heparin plasma, in an effort to evaluate assay performance when analyzing these sample matrices. The preliminary limit of detection studies suggests that the microsieve assay is able to distinguish approximately 6-12ng/mL of sPLA2-IIA from a non-spiked sample. When compared to an immunoassay diluent, the microsieve assay also yielded acceptable percent recoveries for each of the three sample matrices spiked with clinically significant levels of sPLA2-IIA. The sPLA2-IIA microsieve assay prototype also clearly distinguished five samples from septic patients from five normal donor samples, and the results were in good agreement with a comparator ELISA test system (R2=0.9347).

Feasibility of a simple microsieve-based immunoassay platform.

The intrinsic properties of silicon microsieves, such as an optically flat surface, high overall porosity, and low flow resistance have led to an increasing number of biotechnology applications. In this report, the feasibility of creating a microsieve-based immunoassay platform was explored. Microsieves containing 5µm pores were coupled with poly-acrylic acid chains, and then mounted into a plastic holder to enable rapid reagent exchanges via a wicking mechanism. The mounted microsieves were coated with infectious disease-related antigens at [2.5 and 25µg/mL], [20 and 50µg/mL], and [20 and 100µg/mL] to facilitate detection of serum-derived human antibodies against Rubella (3-day measles), B. burgdorferi (Lyme disease), or T. pallidum (syphilis), respectively. The prototype microsieve-based immunoassay platform was able to distinguish positive control sera containing antibodies against Rubella, T. pallidum, and B. burgdorferi from negative control sera with similar qualitative results as FDA-approved ELISA tests. Testing of a WHO IgG syphilitic standard at 0.3, 0.15, 0.075, 0.0375, and 0.01875IU/mL demonstrated that the T. pallidum microsieve assay is able to distinguish disease-specific IgG signal from background signal at similar, and possibly lower, levels than the corresponding ELISA. The T. pallidum microsieve assay prototype also differentiated positive clinical serum samples from negative donor samples, and the results were in good agreement with ELISA (R(2)=0.9046). These feasibility studies demonstrate the potential for utilizing microsieves, along with a reagent wicking device, as a simple diagnostic immunoassay platform.