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Wednesday, 30 September 2020

CLINICAL LABORATORY REPORTS IN AUTOMATED URINARY BIOCHEMISTRY: A PROPOSAL

Written by Macarena Díaz Giménez | Enrique Rodríguez Borja | Arturo Carratalá Calvo

Figure 1. Laboratory report proposal for automated urinary biochemistry.
 
Difficulty in clinical laboratory reports interpretation frequently lies in the elevated number of parameters (clinical tests and calculated values) that are displayed. Reports for automated urinary biochemistry are a good example of this situation.

In order to make easier interpretations, in our lab we decided to divide urinary laboratory reports into three physiological parts based on the renal location where filtration, reabsorption or secretion from each analyte are mainly performed, achieving a complete functional evaluation.
In paragraph “glomerular function”, we find those analites that have free glomerular filtration and negligible reabsortion and secretions rates as in the case of urea and creatinine. With this last one, glomerular filtration rate (GFR) using the CKD-EPI equation is also estimated. Total proteins results are also included in this section. In absence of glomerular pathology, their urinary concentrations are expected to be very low. In addition, there are other specific proteins used to evaluate kidney impairment at this level as albumin, which due to its charge and size it is not usually filtered in normal conditions.

In the section “proximal tubule function”, we report those tests with the highest reabsorption rate asglucose, uric acid and phosphate. In conjunction to these tests, 2-microglobuline give us more information regarding to tubular impairment due to its highest reabsorption rate at this fraction in normal conditions.

Finally, in the paragraph “collecting duct function”, we include most of the electrolytes because many of their active transporters are located here and it is the more susceptible fraction to endocrinological effects. Despite most of these analytes have reabsortion processes along the entire nephron, a good analysis of the electrochemical urinary balance can be performed given that these analytes are responsible for urinary osmolality and final concentration.

In conclusion, these paragraphs could allow us to make interpretative comments to each section automatically in order to improve the quality of clinical laboratory information and the good use of these reports by clinicians. It is recommended that these comments are always harmonized to meet the requirements of ISO 15189.

REFERENCES

  1.  Lamb EJ, Graham R.D. Jones. Kidney Function Tests. En: Rifai N, Horvath AR, Wittwer CT. Tietz textbook of clinical chemistry and molecular diagnostics. St. 6th edition. St. Louis, Missouri: Elsevier; 2018. 479-517.
  2. Chen TK, Knicely DH, Grams ME. Chronic Kidney Disease Diagnosis and Management: A Review. JAMA. 2019 Oct 1;322(13):1294-1304.
  3. Pineda Tenor D, Cabezas Martínez A, Ruiz Martín G. El Laboratorio Clínico 3: Análisis de las Muestras de orina. 1st edition. LABCAM (Asociación Castellano-Manchega de Análisis Clínicos); 2011.

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