Abstract
Early and reliable laboratory diagnosis is very important to guide treatment of and control strategies for a disease. Some technical problems can occur due to laboratory facilities and methodological procedures. Many in vitro diagnoses are based on colorimetric methods such as the quantitative Enzyme- Linked Immuno Sorbent Assay (ELISA), whereby optical density (OD) is compared with a standard curve. The readings of these assays are based on absorption by a spectrophotometric device of light from a narrow or broad spectrum of waves. Objective: The aim of this work was to read the ELISA plate using different spectrophotometry equipment. Methods: Human plasma samples from healthy volunteers (n=50) and volunteers with tuberculosis (n=24) were prepared previously by whole blood incubation in the commercial Interferon Gamma Release Assay (IGRA) for in vitro diagnosis of tuberculosis and then the Interferon ELISA was performed using commercial equipment from the same manufacturer. The ELISA micro plates were read in three spectrophotometers with different filters/wavelengths: 450, 630 and 450 nm. The optical densities were established and analyzed using the manufacturer’s software program. The results of the readings performed at the recommended wavelength were compared with the other two filters/wavelengths. Results: Among the results obtained, 10 samples showed differences in the results of diagnosis. These discrepancies in metrology were associated with differences in the filters/wavelengths and were consequently identified as false results.
Highlights
And reliable laboratory diagnosis is very important to guide treatment of and control strategies for a disease
The aim of this work was to analyze the reading of EnzymeLinked Immuno Sorbent Assay (ELISA) plates by using as a model of metrology analysis the readings in three different spectrophotometers and comparing results, taking in account the original spectro recommended in a newly available commercial kit used for in vitro diagnosis of human tuberculosis in Brazil
Samples were obtained from volunteers non infected [negative TST] (n=35), with active TB [positive bacilloscopy or sputum culture] (n=24) and Latent tuberculosis infection - positive TST (LTBI) (n=15) Figure 1 of one reference tuberculosis hospital (Specialized Bahia State Hospital)
Summary
And reliable laboratory diagnosis is very important to guide treatment of and control strategies for a disease. Many in vitro diagnoses are based on colorimetric methods such as the quantitative EnzymeLinked Immuno Sorbent Assay (ELISA), whereby optical density (OD) is compared with a standard curve. The readings of these assays are based on absorption by a spectrophotometric device of light from a narrow or broad spectrum of waves. Objective: The aim of this work was to read the ELISA plate using different spectrophotometry equipment. Results: Among the results obtained, 10 samples showed differences in the results of diagnosis These discrepancies in metrology were associated with differences in the filters/wavelengths and were identified as false results. Spectrometry is objective and can be automated in various modern devices that are increasingly available and currently accessible
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