Further Studies on the Standardization of Neonatal Bilirubin

Blijenberg, B. G.; Roetering, H. A.; Vos, Annemiek de; Leijnse, B.

doi:10.1515/cclm.1987.25.10.737

Cited by 6 publications

(6 citation statements)

References 4 publications

(2 reference statements)

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“…1). Similar results were reported by Blijenberg (1). Although individual bilimeters show different slopes, these are in practice largely compensated by deviations in the intercepts.…”

Section: Discussionsupporting

confidence: 88%

Calibration of Direct Reading Photometers for the Determination of Neonatal Bilirubin

Brügmann

1990

Clinical Chemistry and Laboratory Medicine

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Bhjenberg et al. (J. Clin. Chem. Clin. Biochem. 25, 737-741 (1987) (1)) proposed that the assigned values of calibrators for the determination of bilirubin with simple direct reading photometers (bilirubinometers or "bilimeters") should be determined on the same type of instrument. For this purpose, the instrument is calibrated with neonatal serum, whose bilirubin concentration is determined with a reference method unbiased by matrix effects. In the present study, this procedure was developed and tested. Bilirubin was determined in capillary plasma (n = 30) and venous serum (n = 31) of newborns. Measurements were made by direct spectrophotometry in 4 bilimeters, and by a micromodification of Vink's spectrophotometric method after dilution with caffeine reagent (Vink et al. Clin. Chem. 34, 67-70 (1988) (2)). When the bilimeters were calibrated with a commercial control serum, using the concentrations quoted by the manufacturer, the results were higher by 13% (plasma) and 19% (serum) than those obtained by Vink's method. These discrepancies practically disappeared when the bilimeter results were recalculated using a calibrator concentration determined according to Blijenberg. Application of the proposed method to other control sera gave assigned values up to 23% lower than those stated by the manufacturers. After calibration of the bilimeters with various neonatal sera (specimens drawn for therapeutic purposes and residues, obtained from the clinical laboratory), differences of about 10% were observed between the assigned values. It is therefore essential to use several sera. Minor differences were found between bilimeters. Practically the same results were obtained using either the procedure of Vink et al. (2) or Doumas et al. (Clin. Chem. 31,1779-1789(1985 (3)) as the reference method. Blijenbergp rocedure can help to reduce interlaboratory imprecision in neontal bilirubin analysis.

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“…1). Similar results were reported by Blijenberg (1). Although individual bilimeters show different slopes, these are in practice largely compensated by deviations in the intercepts.…”

Section: Discussionsupporting

confidence: 88%

Calibration of Direct Reading Photometers for the Determination of Neonatal Bilirubin

Brügmann

1990

Clinical Chemistry and Laboratory Medicine

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“…This may explain, at least partly, why Blijenberg et al (5,9) and other authors (10, 11) found a wide variation of results for values above 300 μιηοΐ/ΐ, even after calibration with standards based on adult serum.…”

Section: Discussionmentioning

confidence: 91%

“…6 publications (1 -4) that this may lead to considerable errors in the results. It was therefore suggested (5) that bilirubinometers should be calibrated with a pool of neonatal sera, using the reference method value as the assigned calibrator value. This procedure leads to a marked improvement in accuracy (3,4), but it is impracticable for most laboratories, for the following reasons.…”

Section: Introductionmentioning

confidence: 99%

Calibrators and Control Samples for Bilirubinometers

Blijenberg¹,

Brügmann²,

Geilenkeuser³

et al. 1993

Clinical Chemistry and Laboratory Medicine

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Summary:The different matrix properties of neonatal serum and commercial control samples can lead to considerable errors in the calibration and control of bilirubinometers. These difficulties can be avoided by calibration with serum from healthy adults which is supplemented with unconjugated bilirubin. But this procedure is impracticable for most routine laboratories.Under certain preconditions, control samples, with bilirubin concentrations determined with correctly calibrated bilirubinometers or spectrophotometers, are also suitable as calibrators. This was established by determination of the bilirubin concentration of 16 different control samples, using both the reference method and correctly calibrated bilirubinometers or spectrophotometers in three or four specialist laboratories. This was also confirmed in several interlaboratory surveys, some involving up to 72 laboratories. The results of these investigations show that a control sample should be used for the calibration of a bilirubinometer only if it meets the following preconditions:1. There should be no significant difference between the bilirubin values determined with the reference method and with a correctly calibrated spectrophotometer or bilirubinometer.2. The bilirubin concentration should lie in the range 230 -300 μηαοΐ/ΐ.The photometric response of bilirubinometers has a limited linear range, so that analytical results greater than 300 μπιοΙ/1 must be rated as basically unreliable.

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“…According to Henry (14), the concentration of carotenoids in healthy fasting serum is only 2-3 μ,ηηοΙ/Ι. Adult sera from jaundiced patients, however, show a different type of spectral absorbance (4,9,15). In contrast to neonatal sera, adult sera with bilirubin concentrations greater than 150 μτηοΙ/Ι always contain bilirubin glucuronide, and under certain circumstances also δ-bilirubin.…”

Section: Statisticsmentioning

confidence: 99%

Verbesserung der Richtigkeit von Bilirubinometer-Ergebnissen

Schlebusch¹,

Röhle²,

Schneider³

et al. 1991

LaboratoriumsMedizin

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Using two methods, i. e. the reference method of Doumas and measurement with a bilirubinometer, bilirubin was measured in 80 neonatal sera, and in 30 sera from healthy adults containing added, unconjugated bilirubin. In the ränge 150-350 / , the regressions of the analytical values were identical. Thus, correct values for neonatal sera can be obtained by the bilirubinometer affer calibration with a pool of adult sera (containing added bilirubin and standardized with the reference method). However, all bilirubinometers show a more or less curved calibration line, so that deviations from accuracy are to be expected at certain analytytical concentrations, depending on the bilirubin content of the calibrator. A calibrator concentration of 250 / is suggested äs optimal. Using the procedure described here, it is possible to test the linear ränge ofindividual bilirubinometers in the routine laboratory. Keywords: bilirubin -neonates -bilirubinometer -reference method -accuracy Zusammenfassung: Die Bilirubinkonzentration in 80 Neugeborenenseren und 30 Seren von gesunden Erwachsenen, die mit unkonjugiertem Bilirubin aufgestockt waren, wurde mit der Referenzmethode nach Doumas und einem Bilirubinometer gemessen. Die Regressionsfunktionen durch die Meßpunkte sind für beide Gruppen im Bereich 150-350 / identisch. Daraus folgt, daß richtige Ergebnisse in Neugeborenenseren mit Bilirubinometern erzielt werden können, die mit einem Pool von aufgestockten Erwachsenenseren unter Verwendung des Referenzmethodenwertes kalibriert sind. Da alle Bilirubinometer eine mehr oder weniger stark gebogene Kalibrationskurve haben, sind jedoch, abhängig von der Kalibratorkonzentration, Abweichungen von der Richtigkeit in bestimmten Meßbereichen zu erwarten. Als optimale Kalibratorkonzentration wird 250 / vorgeschlagen. Mit dem hier beschriebenen Verfahren ist es auch für Routinelaboratorien möglich, den Linearitätsbereich des eigenen Gerätes zu überprüfen. Schlüsselwörter: Bilirubin -Neugeborene -Bilirubinometer -Referenzmethode -Richtigkeit

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Further Studies on the Standardization of Neonatal Bilirubin

Cited by 6 publications

References 4 publications

Calibration of Direct Reading Photometers for the Determination of Neonatal Bilirubin

Calibration of Direct Reading Photometers for the Determination of Neonatal Bilirubin

Calibrators and Control Samples for Bilirubinometers

Verbesserung der Richtigkeit von Bilirubinometer-Ergebnissen

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