Potential Value of Protease Detection Kits in In Vitro Diagnostics and Clinical Testing

Clinical Detection Requirements for Protease Activity in the Coagulation and Fibrinolysis System

The human coagulation cascade involves multiple serine proteases, such as thrombin, factor Xa, and plasmin, whose abnormal activity is closely associated with thrombotic diseases and bleeding tendencies. Currently, clinical laboratories mostly employ chromogenic substrate assays combined with automated coagulation analyzers for activity detection. The principle is similar to that of protease detection kits—enzyme activity is calculated by measuring the absorbance change of the pNA chromophore released after cleavage of a specific substrate. Kits targeting parameters such as thrombin-antithrombin complex and plasmin-α2 antiplasmin complex are already available on the market, generally requiring a photometer equipped with kinetic detection capability. To use protease detection kits for in vitro diagnostics, one must comply with the Provisions for the Registration and Filing of In Vitro Diagnostic Reagents, complete analytical performance evaluation (precision, linear range, interfering substances), and clinical evaluation. It should be noted that any kit intended for diagnostic use must not use expressions such as "100% diagnostic accuracy" or "absolutely reliable" in its promotional materials.

Exploration of Protease Biomarker Detection in Inflammation and Tumors

Certain matrix metalloproteinases (MMPs) and neutrophil elastase are upregulated during inflammatory responses and tumor invasion, and their activity levels are considered to have auxiliary diagnostic value. Researchers have attempted to develop protease detection kits as tools for detecting activity in serum or tissue homogenates. However, due to the presence of abundant endogenous inhibitors in body fluids (such as α2-macroglobulin and tissue inhibitors), what is directly measured is usually "free activity" rather than total enzyme amount; therefore, detection results need to be normalized against total protein concentration or immunological methods. Some modified kits release hidden activity through acid activation or dissociation of complexes, but such procedures may introduce additional variability. From a regulatory perspective, if such kits are intended to obtain medical device registration certificates, sufficient clinical study reports should be submitted, clearly defining the target population, reference intervals, and comparison data with gold standard methods. Unconfirmed claims such as "early diagnosis" or "precise prediction" are strictly prohibited.

Adaptability Analysis of Kits in Point-of-Care Testing (POCT) Scenarios

With the development of microfluidics and dry chemistry, some protease detection kits are being transformed toward POCT applications—for example, detecting metalloproteinase activity in wound exudate using lyophilized reagent strips combined with a portable reader to assist in assessing the healing status of chronic wounds. Such kits typically report results in a qualitative or semi-quantitative manner (e.g., "positive/negative" or "activity level"). Their advantages lie in simple operation and rapid results, but sensitivity and quantitative accuracy are generally lower than those of large laboratory instrument-based methods. For POCT protease detection kits planning to apply for Class II or Class III medical device registration, manufacturers should clearly indicate in the instructions the sample type, operating temperature range, reading time window, and known interfering factors (such as hemolysis, lipemia, bilirubin, etc.), ensuring that users understand the limitations of the test.

Key Compliance Matters from R&D to Clinical Application

When protease detection kits are used as in vitro diagnostic reagents or research reagents, different regulatory frameworks apply. For products intended solely for scientific research, the packaging and instructions must clearly state "For research use only, not for clinical diagnosis." If planning to move toward clinical application, the category must be determined according to the Classification Catalog of Medical Devices (typically Class II or Class III), and registration testing, clinical trials, and system audits must be completed. Promotional materials should not contain comparative assertions such as "equivalent to a certain gold standard," but should use neutral expressions such as "good correlation with commonly used methods." At the same time, labels and promotional language must avoid implying that the product can replace existing confirmatory diagnostic methods.