Assessment of Results from OTA Rapid Tests
We are frequently asked how CR3-Analytik evaluates the results of various OTA rapid tests. There are different providers on the market, offering tests either as test strips (similar to COVID lateral flow assays) or as “immunochromatographic rapid tests.”
We have reviewed a wide range of currently available rapid tests. All claim to enable a very fast verification of compliance with EU limits. In practice, however, all test kits fail in one or more of the following essential steps required for the correct determination of ochratoxin A content:
One of the most important steps in OTA analysis is ensuring the homogeneity of the laboratory sample. The standard method (DIN EN 14132) requires the sample to be ground “until it passes through a 1 mm sieve.” In addition, a sufficiently large and therefore representative sample quantity must be ground (typically 1 kg). While this may still be feasible for roasted coffee, grinding green coffee to this particle size is only possible with expensive specialized equipment.
The next critical point is the sample amount that will actually be tested. To ensure sufficient representativeness, it is again essential to use a minimum sample amount (at least 15 g according to the standard) – this requirement is in some cases significantly undercut by test kits.
The execution of the test is subject to further requirements, which also apply to in-house quality control. Regulation (EU) 2023/2782 “laying down the methods of sampling and analysis for the control of the levels of mycotoxins in food” sets out clear requirements in Annex II for both the so-called “screening method” and the laboratory itself.
The suitability of the method must be demonstrated for the specific matrices “green coffee,” “roasted coffee,” and “instant coffee” through extensive validation data or proficiency testing. This requirement generally exceeds the capabilities of an in-house laboratory. In most cases, the test kit manufacturer performs such validation and provides the corresponding data. While many providers have conducted validations, only a few have done so specifically for green, roasted, or instant coffee.
The EU regulation specifically requires in Annex II regarding method performance: “LOQ: shall be ≤ 0,5*ML and should preferably be lower (≤ 0,2*ML)” In other words, the limit of quantification (LOQ) should be 20–50% of the legal maximum level. Accordingly, test kits should be capable of reliably quantifying 1.5 µg/kg in roasted coffee and 2.5 µg/kg in instant coffee. None of the evaluated tests demonstrate this level of performance in combination with the coffee matrix.
Furthermore, the EU regulation states: “A laboratory shall comply with the provisions of Article 37(4) and (5) of Regulation (EU) 2017/625.” In practice, this means that a laboratory performing such rapid tests should hold full accreditation according to ISO 17025 or operate in accordance with its requirements. Due to the extensive scope, a full overview of the implications is not possible here—however, it should be noted that ISO 17025 goes far beyond a “laboratory ISO 9001” and sets the highest standards for the competence of personnel, instruments, methods, and analytical quality assurance measures.
In summary, while OTA rapid tests may initially appear to be a good idea, a closer look at the practical aspects leads us to strongly advise caution regarding both result quality and compliance when using such systems.