Development and Validation of an Ultrasensitive Procalcitonin Sandwich Immunoassay

Abstract

Procalcitonin (PCT) is well established as a highly specific biomarker for the detection of bacterial infections and sepsis. However, the currently available diagnostic tests are not able to detect very low or very early increases of PCT or even baseline levels in healthy individuals or patients with non-bacterial infections. In order to be able to detect these very low concentrations of PCT, a sandwich immunoassay was developed using high sensitivity Single Molecule Array technology (Simoa). The assay was thoroughly validated and applied to analyze human cerebrospinal fluid (CSF) and serum samples from patients with bacterial or viral meningitis as well as CSF, serum, and K2 EDTA plasma from healthy control subjects. A 50-fold increase in sensitivity compared to the current gold standard assays was achieved, which was sensitive enough for the detection of baseline PCT levels. Both serum and CSF showed significantly elevated PCT levels in patients with bacterial meningitis compared to patients with viral meningitis and the healthy control group. Procalcitonin concentration levels for patients with viral meningitis and the control group could be measured, but were not significantly different. The determination of PCT in the low pg·mL −1 range could help to improve the monitoring of bacterial infectious diseases, as PCT level changes could be detected earlier.

Role of biomarkers in the diagnosis of invasive aspergillosis in immunocompromised patients

“…In the present study, the optimum cut-off value in the diagnosis of IA was > 260 pg/mL for PCT. Our data like other studies [ 8 , 28 , 29 ] showed a low elevation of PCT in patients with IA. The PCT level in patients with IA is lower because Aspergillus species have a tendency for local infection and isolation of this organism from the blood is rare [ 25 ].…”

“…In Robinson et al, after 3 days, a PCT level > 500 pg/mL occurred in 81% (17/21) of the patients with invasive fungal diseases [ 28 ]. The mean PCT concentration in 86 healthy individuals was reported at 15.8 pg/mL by Carcamo and coworkers [ 29 ]. Also, in healthy people, PCT concentration was reported below 50 pg/mL (0.05 ng/ml] [ 29 ] and 100 pg/mL (< 0.1 ng/ml) [ 8 ].…”

“…The mean PCT concentration in 86 healthy individuals was reported at 15.8 pg/mL by Carcamo and coworkers [ 29 ]. Also, in healthy people, PCT concentration was reported below 50 pg/mL (0.05 ng/ml] [ 29 ] and 100 pg/mL (< 0.1 ng/ml) [ 8 ]. Ortega and co-workers reported: in five patients with more than 5 days of persistent fever, the cutoff level was ≥ 3 ng/ml for the diagnosis of IA [ 9 ].…”

Simultaneous Quantitative Detection of IL-6 and PCT Using SERS magnetic immunoassay with sandwich structure

“…At present, the detection methods reported to IL-6 and PCT mainly include enzyme-linked immunoassay(ELISA) [19], chemiluminescent immunoassay(CLIA) [20], lateral flow immunoassays (LFIA) [21], electrochemiluminescence immunofluorescence analysis [22], immunofluorescence amplification luminescence proximity homogeneous assay (AlphaLISA)technology [23] and high-sensitivity single molecule array technology (Simoa) [24] etc. ELISA requires a large amount of time, cost, machinery and professional training; chemiluminescence detection equipment is expensive and has a narrow linear range; and most of the techniques are limited to single-molecule detection, which lacks the efficiency of disease diagnosis.…”