Comparison of refractometer and biuret methods for total protein measurement in body cavity fluids.

The research primarily compares the reliability of refractometers and the biuret method in measuring the total protein in body cavity fluids. The results ascertain the effectiveness of refractometers for protein measurement in clinical samples, even for values lower than 2.5g/dL, contrary to traditional methods.

Objective of the Research

• The study aims to assess the reliability of determining protein concentration in body cavity fluids using refractometry. This method of assessment has been compared to the biuret method, a well-established procedure for protein quantification.

Research Methodology

• The protein concentration in 25 body cavity fluids was determined using two Goldberg type hand-held refractometers. These results were then compared with those obtained through the biuret method.
• Published charts, which convert refraction (r) to protein concentration, were used to determine protein concentration for values less than 2.5 g/dL. Higher protein values were directly read from the instruments.
• The research encompassed 21 peritoneal fluid samples, 2 pleural fluid samples, and 2 pericardial fluid samples from a diverse set of animals, including horses, cattle, dogs, llamas, and a cat.

Research Findings

• The results from the two refractometers closely correlated with the results from the biuret test (P<.001). This correlation was identified using linear regression analysis.
• The slopes from the linear regression analysis were close to 1, indicating a strong direct relationship between the readings from the refractometers and the biuret method.
• The correlation coefficients were greater than 0.977, further emphasizing the linear correlation between the refractometer and biuret method results.

Conclusion

• The study demonstrated that the range for quantifying protein concentration in body cavity fluids by refractometry can be extended below 2.5 g/dL. This extension allows for a more robust quantitative assessment of most clinical samples when compared to the traditional methods.