Early Diagnosis of Sepsis Using Serum Biomarkers

Terence Chan; Frank Gu

Disclosures

Expert Rev Mol Diagn. 2011;11(5):487-496. 

In This Article

Currently Available Assays

Assays for CRP

Various assays have been designed for measuring CRP and are briefly summarized in Table 3.

QuickRead® CRP, an immunoturbidometric assay, and NycoCard® CRP, a chromatographic immunometric assay, are especially interesting for diagnostic purposes because of the fast run times. A study by Zecca et al. compared the two CRP assay kits on neonates with sepsis.[5] Using a CV of 10 mg/l for both kits, the QuickRead CRP kit produced DA values of 97.2% sensitivity, 80.6% specificity, 83.3% PPV and 96.7% NPV, while the NycoCard CRP kit produced DA values of 94.4, 83.3, 85 and 93.8%, respectively, demonstrating that both kits showed similar performance and provided diagnostically relevant results.[5]

Assays for PCT & SAA

Many assays have been developed to measure PCT, mainly manufactured by BRAHMS (they are briefly summarized in Table 4).

Procalcitonin assay developments have notably improved the functional detection limits and run times, such as the recently developed Kryptor and VIDAS assays (BRAHMS). Schuetz et al. reported that the Kryptor and VIDAS systems could be interchangeably used in the clinical setting when using the same CVs.[56] Of note is the semi-quantitative PCT-Q kit, made commercially available by BRAHMS as a point-of-care testing (POCT) kit. Results are indicated by one of four different shades of a red colored band, each of which corresponds to a different range of PCT levels.[43,57] The ranges indicate the possibility and severity of sepsis. Although the kit is designed to require no specialized training to operate and interpret results, the semi-quantitative nature means that test results are subject to the operating technician's interpretation.[57] User difficulties in interpreting results have been reported, and its results only showed moderate agreement compared with the Kryptor assay when used in the clinical setting.[57]

Similar to PCT and CRP, multiple assays exist to measure SAA (Table 5).

It is interesting to note that the LZ TEST 'Eiken' SAA Kit (Eiken Chemical Co. Ltd, Japan) has been cited as a fully automated rapid kit requiring no specialized equipment, with a detection range of 0–386 µg/ml.[28]

Assays for M & AM

Assays measuring M and AM concentrations are predominantly made by Bio-Rad Laboratories. These quick tests already exist because cultures for fungal infections are often insensitive and time intensive.[70] These include: the Platelia Candida-specific antigen and antibody ELISA kit, with manufacturer suggested CVs of 0.5 ng/ml for M and 10 AU/ml for AM;[70] and the Platelia Aspergillus-specific antigen immunoassay, with a manufacturer suggested CV of 1.5 ng/ml for M.[45] There also appears to be an updated version of the assay kit for the Candida species, with manufacturer suggested CVs of 0.25 ng/ml for M and 5 AU/ml for AM.[29] Enzyme immunoassays with greater sensitivities have also been developed.[71]

Assays for IP-10

No quick diagnostic assays for IP-10 are yet available. The assays used in studies utilize different measurement methods, including: a cytometric bead array kit (BD Biosciences Pharmingen, NJ, USA) with a lower limit of 2.8 pg/ml, able produce results in 4 h using 50 µl of plasma;[72] a commercially available sandwich ELISA kit (R&D Systems, MN, USA) with a lower limit of 1.67 pg/ml, able to run on serum;[52] and the Bio-Plex Human 27 Panel (Bio-Rad Laboratories), a multiplex flow cytometry-based assay.[73]

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