Non-Invasive Bilirubin Measurement Techniques
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Non-invasive bilirubin detection
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Non-Invasive Bilirubin Measurement Techniques
- 2. Outline • Introduction • What is Bilirubin ? • Measurement Techniques of Bilirubin and Serum-Bilirubin Level • How Does a Transcutaneous Bilirubinometer Work? • Limitations of Transcutaneous Bilirubinometers • Companies That Produce Bilirubinometer • Conclusion
- 3. Introduction • In preterm infants, hyperbilirubinemia is common and can impair the central nervous system. • The tests available for measuring bilirubin is to collect blood from heel pricking which is painful. • Therefore, there is a need to develop a non-invasive device to detect bilirubin levels.
- 4. What is Bilirubin ? • Bilirubin is an open chain molecule containing four pyrrole-like rings that forms during the breakdown of heme. • Bilirubin is excreted in urine and bile and can also be found in low levels in plasma. • Eventually, bilirubin is degraded in the liver to be removed from the body.
- 5. What is Bilirubin ?
- 6. Measurement Techniques Of Bilirubin And Serum-Bilirubin Level
- 7. Measurement Techniques Of Bilirubin And Serum- Bilirubin Level Table 1. Bland and Altman comparison and correlation analysis (R, P) and for estimation of the accuracy of bilirubin measurement by transcutaneous bilirubin (TcB) using BiliChek and optical imaging (ToB) using BiliCapture versus automated laboratory bilirubin measurement (TSB).
- 8. Measurement Techniques Of Bilirubin And Serum-Bilirubin Level • Bilirubin Assay Kit (Total and Direct, Colorimetric) Figure 1. Total and Direct Bilirubin concentrations in Normal Human Serum. • Utilizes the Jendrassik-Grof principle to detect bilirubin. • Total bilirubin (unconjugated + conjugated) concentration is determined in the presence of a catalyst, where bilirubin reacts with a diazo-salt to form azobilirubin, which absorbs at 600 nm. • Direct bilirubin (conjugated) is determined in the absence of catalyst (550 nm).
- 9. Measurement Techniques Of Bilirubin And Serum- Bilirubin Level • Transcutaneous Bilirubinometry TcB • Transcutaneous bilirubinometry works basically by directing light into the skin and measuring the intensity of the wavelength of light that is returned.
- 10. Measurement Techniques Of Bilirubin And Serum-Bilirubin Level • BiliCapture optical imaging • It is done with conjunctival image was captured using a camera. • This image is then shared on tablet with the BiliCapture software installed. • With the help of this software, the particular area of interest in the eye showing more yellow color is demarcated and later on estimated for the bilirubin value.
- 11. How Does a Transcutaneous Bilirubinometer Work? • The meter analyzes the spectrum of optical signal reflected from the neonate’s subcutaneous tissues. • These optical signals are converted to electrical signal by a photocell. • These are analyzed by a microprocessor to generate a serum bilirubin value.
- 12. How Does a Transcutaneous Bilirubinometer Work? • The available meters can be divided into 2 categories: (i) Multi wavelength Spectral Reflectance meters (Bilicheck) (ii) Two-wavelength (460 nm, 540 nm) Spectral Reflectance meters (Minolta, Bili-test)
- 13. How Does a Transcutaneous Bilirubinometer Work? Figure 2. Measurement principle of JM-103. (Drager Medical)
- 14. How Does a Transcutaneous Bilirubinometer Work? Figure 3. Measurement principle of BiliChek.
- 15. How Does a Transcutaneous Bilirubinometer Work? • The basic principle remains the same for each transcutaneous bilirubinometer. • The optic head of the meter is gently pressed against the neonates skin (usually forehead or upper part of sternum). • For correct measurement, the optic head should make full contact with the skin. http://www.sumertek.com/bilicare
- 16. Companies That Produce Bilirubinometer Table 2. Common transcutaneous bilirubinometer available in the market. S.No. Make Principals Dealers Cost 1. Airsheild’s- Minolta Hillrom-Airsheild’s Drager Medical Rs. 1,00,000/- 2. Bilitest Technomedia Lacteromedik Pharmamen Enterprises Rs. 1,20,000/- 3. BiliChek Spectrex Rustagi Surgicals, Phoenix Rs. 1,75,000/- 4. Ohmeda Datex- Ohmeda Phoenix Not launched 5. BiliCare Gerium Mennen Medical Not launched 6. Jaundice Meter JM-105 Minolta/Hill-Rom Air-Shields) Drager Medical Not launched
- 17. Limitations of Transcutaneous Bilirubinometers • TcB can be affected by a variety of factors, such as phototherapy and exposure to sunlight. • Dermal thickness and the melanin content of the skin. • Limit the use of TcB to infants <10 days old. • A clean, disposable tip is required for each measurement.(BiliChek)
- 18. Conclusion • Non-invasive TcB measurements are a desirable modality since it is a quick, non-invasive technique to screen for hyperbilirubinemia. • As a substitute to TSB for inspecting jaundiced neonates. • It reduces invasive blood sampling and permits a time effective and reasonably precise estimation of bilirubin levels. • None of the actual guidelines suggests the use of TcB measurements as an indication for starting phototherapy.
Editor's Notes
- Bilirubin is a yellowish substance in your blood. It forms after red blood cells break down, and it travels through your liver, gallbladder, and digestive tract before being excreted. Typically, bilirubin levels fall somewhere between 0.3 and 1.2 milligrams per deciliter (mg/dL). Anything above 1.2 mg/dL is usually considered high. The condition of having high bilirubin levels is called hyperbilirubinemia. It’s usually a sign of an underlying condition, so it’s important to follow up with a doctor if test results show you have high bilirubin. Many babies are also born with high bilirubin, causing a condition called newborn jaundice. This causes yellow-tinted skin and eyes. It happens because, at birth, the liver often isn’t yet fully able to process bilirubin. This is a temporary condition that usually resolves on its own within a few weeks.
- Unconjugated (indirect): When the heme is released from hemoglobin (during red blood cell breakdown), the remainder is converted to unconjugated hemolgobin. This form of bilirubin travels from the bloodstream to the liver. This molecule is not water soluble. Conjugated (Direct): Bilirubin is converted from unconjugated to conjugated bilirubin in the liver. This happens when sugar attaches to the unconjugated bilirubin. The unconjugated bilirubin turns into bile and enters the small intestines. It is eventually eliminated through a person's stool. This molecule is water soluble.
- Different volumes of human serum (10 - 50 µL) were assayed following kit protocols. Reported concentrations (in mg/dL): Total Bilirubin: 4; Direct Bilirubin: 1.5. Experimental concentrations (calculated as the average of estimated bilirubin in five different human serum volumes ranging from 10 to 50 µL): Total: 3.8 mg/dL; Direct: 1.75 mg/dL. Because blood collected from newborns is often hemolysed, this could affect the accuracy of the clinical laboratory methods.
- These meters work by directing light into the skin of the neonate and measuring the intensity of specific wavelength that is returned. The number of wavelengths, used is variable in different transcutaneous bilirubinometers. The meter analyzes the spectrum of optical signal reflected from the neonate’s subcutaneous tissues. These optical signals are converted to electrical signal by a photocell. These are analyzed by a microprocessor to generate a serum bilirubin value. The major skin components, which impart the spectral reflectance in neonate, are (i) melanin, (ii) dermal maturity, (iii) hemoglobin, and (iv) bilirubin.
- Earlier, the transcutaneous bilirubinometers utilized only a few wavelengths. In these meters, there was no provision to overcome the impact of dermal maturity and melanin content. Therefore, separate analysis for each patient population (different ages and races) was required one had to refer to different conversion tables for each population. However, a new product, BilicheckTM (Specter, Inc) performs a spectral analysis at more than 100 different wavelengths. By subtracting the spectral contribution of the known components, the bilirubin absorbance is quantified. The available meters can be divided into 2 categories:
- The JM-103 determines the yellowness (bilirubin) of the subcutaneous tissue of a neonate by measuring the difference in the optical densities of reflected light at 450 and 550 nm by the newborn skin. With this method, 2 optical paths are incorporated into a measuring probe that minimizes the interference due to melanin or skin maturity. When the light returns to the fiber, it is scattered from shallow areas of subcutaneous tissue and passes through the inner core (short optical path) of the fiber, whereas the light scattered from deep areas of subcutaneous tissue pass through the outer core (long optical path). The reflected light is then collected by photodiodes. Because there is a linear correlation with TSB and the difference in the absorbance, the TSB can be estimated. Reproduced with the permission of Draeger Medical Systems, Inc., Telford, PA
- Schematic of the reflection of light emitted by a tungsten halogen lamp by the newborn skin. A proprietary algorithm is used to analyze the collected light. The device measures the bilirubin transcutaneously by using visible light (380–760 nm) reflected by the skin. The light absorption of interfering factors, such as hemoglobin, melanin, and dermal thickness, is mathematically subtracted to estimate the bilirubin concentration in the capillary beds and subcutaneous tissue. IR, infrared; A/D, analog-to-digital; DA/MO, days/months; LCD, liquid crystal display; OD, optical density (A, absorbance). Reproduced with the permission of Philips/Children’s Medical Ventures, Monroeville, PA.
- The basic principle remains the same even if each transcutaneous bilirubinometer has a different detailed operating procedure. The optic head of the meter is gently pressed against the neonates skin (usually forehead or upper part of sternum). For correct measurement, the optic head should make full contact with the skin and there should be no gaps between the head and the skin. This should be achieved by gentle pressure.
- Although TcB measurements have been shown to correlate well with TSB, TcB can be affected by a variety of factors, such as phototherapy and exposure to sunlight (28, 36, 37 ). The algorithms that transform the TcB measurements into a bilirubin concentration use estimates of hemoglobin concentrations, which decrease approximately 10% in the first week of life, along with dermal thickness and the melanin content of the skin, both of which are known to impact TcB measurements (38, 39 ). This has led most facilities to limit the use of TcB to infants 10 days old. However, preliminary studies on the use of TcB to identify adults at risk of liver dysfunction by Harbrecht et al. (40 ) suggest that TcB may be used on much older newborns, although this observation will require additional confirmatory studies. Care must also be taken to avoid testing skin that is bruised, has a birthmark, or is covered with hair. a clean, disposable tip is required for each measurement, substantially increasing the cost of the test
- Systematic reviews concluded that TcB devices reliably estimated bilirubin levels in term and preterm infants but none of the actual guidelines suggests the use of TcB measurements as an indication for starting phototherapy.