BILITEST
Non invasive transcutaneous hyperbilirubinemia analyzer.

RECOMMENDATIONS FOR CLINICAL USE

1. INDICATION
The intended use of the BILITEST Hyperbiliruinemia Analyzer is to screen newborn infants for hyperbilirubinemia, including:

  • to determine the degree of jaundice and to monitor its dynamics;
  • to identify newborn infants whose degree of hyperbilirubinmia indicates that a serum bilirubin test is (is not) necessary;
  • to assess the therapy efficiency.
2. MESUREMENT PRINCIPLE
High correlation between noninvasive measurement results of bilirubin concentration in derma and bilirubin concentration in blood has provided the basis for promoting Method of Transcutaneous Bilirubinometry into medical practice. This concept has been embodied in the BILITEST Hyperbilirubinemia Analyzer.
The correlation is caused by existing dynamical balance between bilirubin concentration in blood and subcutaneous tissues due to reversible diffusion of a bilirubin between blood and tissues.
High level of bilirubin concentration in blood leads to a high bilirubin concentration in derma and vice versa - low level of bilirubin concentration in blood (for example, during exchange transfusion) results in bilirubin counterblow from tissues to blood until the balance between these to bilirubin reserving systems is reached.
It is important that after such therapeutic measures as phototherapy and exchange transfusion a balance between these two bilirubin reserving systems is reached as a rule within 5 - 6 hours.

 

3. BILITEST FEATURES
The BILITEST is a portable fully automated photometer. Its operation is based on the principle of two-wave skin reflectance measurements. It analyses spectrum of optical signal reflected from infant’s subcutaneous tissues. The BILITEST makes it almost unfeasible for light detectors to record the skin colour influence upon the results.
In essence the BILITEST determines bilirubin concentration in derma through the use of subcutaneous tissues photometry. Because there are no reference materials for bilirubin concentration in derma, the device is calibrated by convention in units of Transcutaneous Bilirubin Index (TBI) following the international practice.

4. OPERATING PROCEDURE
Transcutaneous Bilirubinometry Operating Procedure is rather simple with the use of the BILITEST hyperbilirubinemia analyzer. The BILITEST optic head is gently pressed against infant’s skin (usually forehead or upper part of sternum). The measuring procedure of the BILITEST lasts for 2 - 3 seconds and is accompanied by a soft sound. When the sound has finished, the procedure is over. The BILITEST digit display reads the result. The device is now ready for anther measurement. Display keeps the result of single measurement for about 60 seconds then automatically erases it and the device is switched to the standby mode. The device is in the standby mode until following measurement.
The verification of device’s performance should be made before and after run measurements, using two Control Reading Checkers.

WARNINGS

In case the readings are supposed to be incorrect it is recommended to perform three additional measurements at a time. If three obtained readings differ, the average value should be chosen, the least and the greatest exempted. To avoid Hyperaemia anther part of infant’s skin should be chosen for repeat measurement. Hyperaemia may influence the result.
Avoid measurements against Bruising, Birthmarks and subcutaneous Hematoma.

5. ESTIMATION OF SERUM BILIRUBIN CONCENTRATION USING THE BILITEST READINGS
The BILITEST is calibrated so that the value of TBI multiplied by 10 approximates the value of serum bilirubin concentration, if TBI measuring is made against infant’s forehead. Normally the real serum bilirubin concentration doesn’t differ from corresponding estimation more than 35 m mol/l.

WARNING

One should remember that in a number of clinical cases, described in subsection 6, the balance between bilirubin concentration in blood and in subcutaneous tissues is disrupted. In these cases, serum bilirubin testing is needed and the use of the BILITEST for estimation of the serum bilirubin concentration is not recommended.

NOTES

  1. The BILITEST has been calibrated for the newborn infants without intensive skin pigmentation (for European race).
    In other cases correspondence between TBI and serum bilirubin concentration values should be refined. The User refine it himself, comparing the readings of the BILITEST with the corresponding laboratory data of serum bilirubin testing.
  2. To obtain calibration coefficients for the BILITEST the bilirubin concentration in blood was measured with the help of two-wave photometrical method. The newborn capillary blood plasma was put through a direct photometrical process. Near 300 newborn infants, gestational age of 30 - 40 weeks and weight of 1400 - 3500 g, were examined. In parallel with determination of bilirubin concentration in blood, all the infants were examined for TBI on forehead, on upper part of sternum and inner surface of leg. Correlation coefficients between bilirubin concentration in blood and corresponding TBI values were equal to: r = 0.92 for forehead; r = 0.86 for sternum; r = 0.54 for leg inner surface.
    Because the best correlation between TBI and bilirubin concentration in blood was shown on forehead, the corresponding data had been chosen for the BILITEST calibration. Measuring TBI on forehead also allows infant’s examinations to be performed without additional manipulations with the newborns (e.g. taking clothes off).
  3. To estimate the reproducibility of the BILITEST’s readings 76 infants were examined. During examination, every infant was subjected to measurement 5 times and CV% for each of it was calculated.
    The results of examination were the following:
  • imprecision (CV%) of TBI readings averages 4 percent (varies from 2 to 5 percent sometimes amounting to 7 percent);
  • imprecision of the device itself (on Reading Checkers) does not exceed 2 percent.
The good reproducibility of the BILITEST allows carrying out TBI measurements only once for every infant in clinical use.
The examinations have shown that medical staff (even with a little experience) can use the BILITEST.

 

6. TRANSCUTANEOUS BILIRUBINOMETRY FEATURES
One should bear in mind that the result may be incorrect if measurements are carried out against bruising or subcutaneous hematomas (for example, after infusion therapy). In this case, the TBI measurement is preferable to be made on the upper part of sternum.
While measuring TBI of the low weight newborns who suffer from hemodynamics disorder and are in severe somatic state, the Hyperaemia spot appears in the area where the device's optic head is pressed against the skin. Repeat measurements against this area show overestimated results due to emerged local stasis of the blood. Although such spot vanishes quickly, repeat measurements are recommended to be made on near-by locations.
When phototherapy is used, photooxidation of bilirubin takes place and it is converted into water-soluble non-toxic lumirubin form. In this case, direct correlation between bilirubin concentration in subcutaneous tissues and in blood is not quoted. Thus, TBI determination during phototherapy does not permit to assess the bilirubin concentration level in blood. However, the estimation of newborn phototherapy efficiency can be made based on the dynamics of the BILITEST's readings during the whole treatment period.
In case of haemolytic disease of newborn infants the BILITEST should not be used to assess bilirubin concentration in blood because the rate of bilirubin penetration growth due to intensive intervascular hemolysis. In this case, even relatively small TBI values need bilirubin level control in the blood to be carried out.

7. JAUNDICE TREATMENT USING THE TBI MEASUREMENT RESULTS
In Case Of Jaundice, it is recommended to carry out TBI measurements not less than 4 times a day to control the disease dynamics and therapy efficiency.
Premature infants (having weight less than 1500 g) are recommended to receive phototherapy if TBI value equals 12-15, as they are highly sensitive to bilirubin and lower bilirubin concentration may cause Encephalopathy. As a rule, if on the second-fourth day of an infant's life TBI value exceeds 15, this point out to serious illness and demands combined conservative treatment.
If TBI value is more than 20, one should control bilirubin concentration growth in blood and make measurements every hour. The same recommendations can be used if TBI value exceeds 20 and 25 on the 4th-7th day correspondingly. In case TBI value is more than 27-30, an urgent serum bilirubin testing is needed (with fractions of bilirubin).

WARNINGS

If there is no Jaundice, it is impossible to assess bilirubin concentration in blood using TBI values. It is necessary to determine bilirubin concentration in venous and umbilical blood of the newborn, who run the danger of haemolytic disease, in order to make decision on exchange transfusion during the first day.
REMEMBER that estimation of bilirubin levels in blood using the TBI readings is approximate. If exchange transfusion is thought to be made, serum bilirubin concentration measurement is needed.