RECOMMENDATIONS FOR CLINICAL USE
The intended use of the BILITEST Hyperbiliruinemia Analyzer is to screen newborn infants for hyperbilirubinemia, including:
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 infants 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 (TcBI) following the international practice.
Transcutaneous Bilirubinometry Operating Procedure is rather simple with the use of the BILITEST hyperbilirubinemia analyzer. The BILITEST optic head is gently pressed against infants 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 devices performance should be made before and after run measurements, using two Control Reading Checkers.
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 infants 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
The BILITEST is calibrated so that the value of TcBI multiplied by 10 approximates the value of serum bilirubin concentration, if TcBI measuring is made against infants forehead. Normally the real serum bilirubin concentration doesnt differ from corresponding estimation more than 35 m mol/l.
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.
- imprecision (CV%) of TcBI 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 TcBI 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 TcBI measurement is preferable to be made on the upper part of sternum.
While measuring TcBI 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, TcBI 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 TcBI values need bilirubin level control in the blood to be carried out.
7. JAUNDICE TREATMENT USING THE TcBI MEASUREMENT RESULTS
In Case Of Jaundice, it is recommended to carry out TcBI 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 TcBI 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 TcBI value exceeds 15, this point out to serious illness and demands combined conservative treatment.
If TcBI 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 TcBI value exceeds 20 and 25 on the 4th-7th day correspondingly. In case TcBI value is more than 27-30, an urgent serum bilirubin testing is needed (with fractions of bilirubin).
- If there is no Jaundice, it is impossible to assess bilirubin concentration in blood using TcBI 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 TcBI readings is approximate. If exchange transfusion is thought to be made, serum bilirubin concentration measurement is needed.