# Analytical evaluation of the performances of point-of-care and benchtop procalcitonin assays in comparison with the B⋅R⋅A⋅H⋅M⋅S PCT sensitive KRYPTOR assay

## TL;DR

This study compares the accuracy of several procalcitonin tests against a standard reference test, finding that some perform poorly at low concentrations, which could affect diagnosis.

## Contribution

The study provides a detailed analytical comparison of non-standard procalcitonin assays against the B⋅R⋅A⋅H⋅M⋅S reference standard.

## Key findings

- Wondfo, Getein, and Snibe assays showed higher imprecision compared to the KRYPTOR assay.
- Wondfo and Getein assays exceeded allowable deviation from linearity and showed significant bias.
- Snibe showed better agreement but still had limitations in low-range PCT concentrations.

## Abstract

Procalcitonin (PCT) is increasingly utilized in clinical laboratories, leading to the proliferation of commercial PCT assays. However, not all of these assays are traceable to the B⋅R⋅A⋅H⋅M⋅S PCT standard, which is integral to established PCT clinical algorithms. This study evaluates the suitability of three non-B⋅R⋅A⋅H⋅M⋅S PCT assays for the application of these algorithms.

The study assessed PCT assays from Wondfo (PCT-W), Getein (PCT-G), and Snibe (PCT-S), comparing them to the B⋅R⋅A⋅H⋅M⋅S PCT sensitive KRYPTOR assay (PCT-KR). Analytical performance, including linearity, imprecision, and recovery, was evaluated. Additionally, a method comparison study involving 350 routine serum samples was conducted to assess agreement, bias, and correlation with the KRYPTOR assay.

The KRYPTOR assay exhibited a maximum imprecision of 4.65%, while Wondfo, Getein, and Snibe showed higher imprecision at 8.38, 10.25, and 15.67%, respectively. Wondfo and Getein assays exceeded the maximum allowable deviation from linearity, and the Snibe assay failed the recovery assessment. Passing-Bablok regressions for low-range samples indicated significant bias for Wondfo (PCT-W = 0.663 PCT-KR + 0.076) and Getein (PCT-G = 0.838 PCT-KR−0.06). Agreement with the KRYPTOR assay was Kc = 0.83 and Kc = 0.87 for Wondfo and Getein, respectively, with substantial agreement in lower respiratory tract infections (LRTI) at Kc = 0.78 and Kc = 0.65. The Snibe assay showed better overall agreement (PCT-S = 1.002 PCT-KR−0.069), with Kc = 0.92 for sepsis and Kc = 0.76 for LRTI.

Despite high overall agreement with the KRYPTOR assay, the evaluated assays (Wondfo, Getein, and Snibe) exhibit insufficient analytical performance at low PCT concentrations, which may limit their reliability in the diagnosis and management of sepsis and LRTI.