Response of Blood Urea using RF Scalar Network Analyzer

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21st Mar 2018 Medical Reference this


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“2015 International Conference on Technologies for Sustainable Development (ICTSD-2015), Feb. 04 – 06, 2015, Mumbai, India”

Ingrid Anne P. Nazareth, Rajendra S. Gad, Sulaxana R. Vernekar, Gourish M. Naik


AbstractUrea content in the human blood is an important parameter to monitor the healthy state of a human being. Normally a patient is sent to pathological laboratories for blood extraction to quantify the actual urea percentage. Although this method is accurate, it requires a lot of time and reagents. It also involves the fear of infection during the extraction of blood. The method described in this manuscript gives a simple technique based on RF response of urea in the human tissue. In this paper, laboratory samples of various urea percentages were prepared and their responses were measured using a RF dielectric loss cell. The setup consists of a signal generator and a spectrum analyzer connected in scalar network mode to measure the RF response from 10MHz to 500MHz. The results show that there is a linear relation between the dielectric loss and the percentage of urea in the sample.

KeywordsUrea, Health, RF Spectroscopy, Multivariate Regression.


Health is a condition of entire physical, social, and mental well being, and not exactly the absence of disease or infirmity.[1]-[3] Good Health or healthy living inhumans beings is the generally the normal condition of aperson’s body and mind, which means to be free fromillness,painor injury.[1] Health care providers promote good health in humans as well as prevent or cure health problems. A number of other factors like the “determinants of health” can also influence the health status of persons, which include lifestyle, background, social and economic conditions. High levels of stress can also affect health tremendously.[4]

Health is often marred by illnesses and diseases sometimes curable, sometimes incurable.[5] The disease can affect any part of the body for which there are medications available accordingly. One of the most important organs are the kidneys in which urea is a primary components of urine which is filtered by them.

The handling of urea by the kidneysis an important part of mammalian metabolism. Urea has various roles to play including thecounter current exchange systemof thenephrons which reabsorbs water and critical ions from the excretedurine and as a carrier of waste nitrogen.

The conversion factor 0.028 g/mmol can be used to estimate the equivalent nitrogen content (ingram) of urea (inmmol).[6]Subsequently, 1gram of nitrogen is approximately equivalent to 6.25grams ofprotein, and 1gram of protein is more or less equivalent to 5grams ofmuscletissue. 1mmol of excessive urea in the urine, measured by urea concentration in mmol/l multiplied by urine volume in litres roughly equals to a muscle loss of 0.67gram in conditions of muscle wasting.

Uraemiaor uremia which means “urea in the blood” can be defined as a surplus of protein and amino acid metabolism end products (urea andcreatinine) in the blood that is usually excreted in the urine.[7] Symptoms of uremia include fatigue, weakness, nausea and vomiting leading to loss of appetite,[8] muscle wasting, shallow respiration, metabolic acidosis, tremors and abnormal mental function. In case dialysis or kidney transplant is not carried out, uremia will lead to renal failure causing stupor, coma and ultimately death. [9][10]One of the Potential Uremic Toxins is urea present at high concentrations i.e. >300mg/dL or >50mmol/L. The effect of high uremic toxins are headaches, vomiting, fatigue, carbamylation of proteins.[10]

The onset of uremia is untimely for people who have kidney disorder. People who are over 30 years old and have a kidney function below 50% (Glomerular Filtration Rate [GFR] from 50 to 60 mL) are inclined to have a high degree of uremia. Incidentally in the United States, around 8 million people have uremic symptoms with a GFR of <60 mL. [11]The diagnosis of renal dysfunction can be difficult when the symptoms such as fatigue can be imprecise. Dialysis or a renal transplant would be possibly the best treatment. [11]

  1. Blood tests

Primary tests performed for the diagnosis of uremia arebasic metabolic panelwith serumcalciumandphosphorusto evaluate theGFR,blood urea nitrogenand creatinineas well as serumpotassium,phosphate,calciumandsodiumlevels. Uremia will show high levels of urea and creatinine, high phosphate, normal or slightly high sodium, likely depressed calcium levels and elevated potassium. The physician will check foranemia, thyroid and parathyroid functions in a basic routine test. A warning sign of established renal failure is chronic anemia. Calcium abnormalities can be determined by the thyroid and parathyroid panels as they are related to uremia as longstanding or unrelated illness of calcium metabolism, as well as work up any symptoms of fatigue.

B. Urine tests

In order to determine urea and creatinine clearance, a 24 hour urine collection may be an alternative but not be a very precise test due to the collection procedure. Alternate laboratory tests, that should be considered for the presence of blood casts, pH and protein, areurinalysiswith microscopic examination.[12]

  1. Methodology

The constituents like Urea whose frequency responses are to be measured are dissolved in a known quantity of distilled water. The multivariate and curve-fitting statistical applications can model the multi-frequency bio-electrical impedance spectrum to develop parameters to estimate body composition like Urea, Cholesterol, Glucose etc.[13] The principle behind the response of these constituents is based on absorption of EM energy by various molecular vibrations in the sample.

  1. Preparation of samples

Urea ranges from 10-20 mg/dL. Average concentration of urea i.e. 15 mg/dL was used in the preparation of samples. The solution samples were prepared using double distilled water with half, normal, double and triple concentrations of urea. All the above said concentrations of urea were dissolved in 1 mL of Alcohol and 14 mL of water. Experiments were performed in fast sweep mode followed by the slow sweep mode. The experiment was repeated twice with a gap of one hour and two hours, to invalidate the environmental effect. Both the results were compared to the initial results and were found to be accurate with a slight error.

  1. Cell Design

A cell was fabricated with a length of 12.5cms, breadth of 1cm and height of 2cms. The inside and outside of the cell was lined with a thin copper foil which was then grounded. In order to prevent external radiation, the cell was placed in an iron container which was grounded.[14] The tracking generator, cell and signal analyzer were fastened onto a wooden plank to prevent any displacements as shown in Fig. 1. The tracking generator used is the ‘Signal Hound tracking generator’ and the signal analyzer used is the ‘Signal Hound Signal Analyzer’.

  1. Impedance measurement

Signal is injected at connector 1 at one end of the cell from the Tracking Generator and then transmitted through the liquid column and observed at connector 2 at the other end of the cell.

Fig. 1: Experimental Setup

  1. Results

By using the above setup, the typical graph is recorded as shown in Fig. 2. The RF spectra is shown from 10 MHz to 500 MHz continuously.


Fig. 2: RF spectra from 10MHz to 500MHz

Though the graph shown in Fig. 2 for all Urea concentrations which have a behaviour similar to that of the RF response of water, there is a subtle change in the attenuation level for urea at some points and its neighbourhood, some of which are given in Table I. Though concentration 3Urea is the extreme level of composition in the human blood, yet it was taken for investigation to see the observable changes in the absorption pattern for urea concentration. Since the variation were observed at the frequencies given in the table, it is always possible to extrapolate the concentration of urea to other concentrations which are normally found in the human blood. The table given below is very important when the estimation of the urea has to be done more quantitatively using mathematical regression tools. One such method is called multivariate regression technique for which these frequency points and corresponding attenuation can be fed as variables and the estimation of urea can be done for unknown sample concentrations. The work is in progress.


Variation of Attenuation level of Urea in dB

Freq in MHz





































  1. Conclusion

The manuscript describes an experimental technique to determine the urea concentration using RF response cell. The results obtained in the experiment show that the technique is useful for determining unknown concentrations of urea in any given blood sample non-invasively. The results shown are for laboratory prepared samples with Urea as major constituent and not actual blood sample which contain over 100 constituents. The method can be extended further to incorporate other constituents and can be actually compared with blood samples. The technique is useful in estimating urea concentration using multivariate system approach which is a purely mathematical tool. The combination of this tool with the above findings can develop into a full fledge instrumentation for determining blood urea concentration non-invasively.


Since a scholarship for the above work was provided by the Goa University, author Ingrid Anne P. Nazareth wishes to thank them profusely.


  1. Grad, Frank P. “The Preamble of The Constitution of The World Health Organization”.Bulletin of the World Health Organization, Vol. 80, No.12, 2002, pp: 981-982
  2. “Dictionary – “Health””.Merriam-Webster. Retrieved 21 April 2011.
  3. World Health Organization. 2006.Constitution of the World Health Organization–Basic Documents, Forty-fifth edition, Supplement, October 2006
  4. Walter F. Boron “Medical Physiology: A Cellular And Molecular Approach” Elsevier/Saunders, pp: 837
  5. Anuja Pandey, Sanjay Zodpey, Sunanda Shrikhande, Anjali Sharma, “Human Resource Capacity Building Initiatives for Public Health Laboratories in India”, Indian Journal of Public Health, Vol 58, Issue 4, October-December 2014, pp: 224-229
  6. Jacki Bishop, Thomas, Briony, “Manual of Dietetic Practice”, Section 1.9.2 Wiley-Blackwell, 2007. p: 76
  7. G.A. Martinez, “Measuring System of Urea in Blood by Application in Recirculation for Hemodialysis” in Treatment, Technical Problems in Patients on Hemodialysis, chapter 13, 2011, pp:215-227
  8. Juan Jesús Carrero, Pharm, Abelardo Aguilera, Peter Stenvinkel, Fernando Gil, Rafael Selgas, Bengt Lindholm, “Appetite Disorders in Uremia” Vol 18, Issue 1, January 2008, pp:107-113
  9. Bishop, M.L. Fody, E.P. and Schoeff, L.E. “Clinical Chemistry: Techniques, Principles, Correlations.” 6th Edition. Lippincott Williams and Wilkins. p: 268.
  10. Burtis, C.A.; Ashwood, E.R. and Bruns, D.E. Tietz “Textbook of Clinical Chemistry and Molecular Diagnostics.” 5th Edition. Elsevier Saunders. p.1554
  11. Timothy W. Meyer, and Thomas H. Hostetter, “Uremia” N Engl J Med 2007; Vol 357, No. 13, September 27, 2007 ,pp:1316-1325
  12. Uremia Workup. A Brent Alper Jr. Medscape. Accessed at
  13. I.A.P. Nazareth, S.R.Vernekar, R.S. Gad, G.M. Naik, “An Algorithm for Estimation of Blood Cholesterol based on Regression Technique”, International Journal of Advanced Research in Computer Science and Software Engineering (IJARCSSE), Vol. 4, Issue 8, August 2014, pp. 758-761
  14. I.A.P. Nazareth, S.R. Vernekar, R.S. Gad, G.M. Naik, “Application of RF Spectroscopy for Blood Glucose Measurement” International Journal of Electronics and Communication Engineering & Technology (IJECET), Vol. 5, Issue 7, July 2014, pp. 32-38

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