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 (TcBI) 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 TcBI
multiplied by 10 approximates the value of serum bilirubin
concentration, if TcBI 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
The BILITEST has been calibrated for the newborn infants
without intensive skin pigmentation (for European race).
In other cases correspondence between TcBI 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.
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 TcBI on forehead, on upper part of sternum
and inner surface of leg. Correlation coefficients
between bilirubin concentration in blood and
corresponding TcBI 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 TcBI and bilirubin
concentration in blood was shown on forehead, the
corresponding data had been chosen for the BILITEST
calibration. Measuring TcBI on forehead also allows
infant’s examinations to be performed without
additional manipulations with the newborns (e.g. taking
clothes off).
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 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).
WARNINGS
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.
4.
OPERATING PROCEDURE