PEDIATRICS Vol. 111 No. 4 April 2003, pp. 919-920
Measuring Bilirubin Through the Skin?
To the Editor.—We commend Engle et al for their study of a large Dallas Hispanic population with elevated bilirubin levels.1 Visual assessment of jaundice is particularly challenging in this population. Before all differences between cutaneous bilirubin and total serum bilirubin (TSB) are ascribed as errors in transcutaneous (TcB) measurement, we must acknowledge TSB measurement is also susceptible to errors of similar magnitude in a clinical laboratory.2
Quality control of their TSB measurements (using the College of American Pathologists’ guidelines) was limited to a few samples sent to an independent laboratory for high-performance liquid chromatography (HPLC) analysis (gold standard). Differences between clinical method and HPLC analysis were reported as usually <1.0 mg/dL, but 27% of the time (7/26) the differences were between 1 and 1.9 mg/dL. Though clinically acceptable, its importance should not be underestimated. Blood sample collection and handling are additional sources of error in any laboratory measurement, even by experienced clinicians. These types of error in the TSB assay would not be detected by sending the serum samples to 2 separate laboratories, but it would introduce a difference between TcB and TSB measurements.
We agree with the authors’ statement that "... a TSB value >10 mg/dL certainly would be cause for concern in a 24- to 36-hour-old infant being discharged from the hospital, whereas the higher value (>15 mg/dL) might be of more relevance in an older infant being seen in follow-up." We recommend that this logic be utilized in the assessment of the sensitivity and specificity analysis, ie, instead of applying cutoff values of 10 to 15 mg/dL, the bilirubin level of interest should be determined for each patient, at the time of the measurement(s), based on their respective postnatal age, using the hour-specific bilirubin nomogram2–4 or by established AAP guidelines.5 The author’s data could also improve our understanding of the serum-skin bilirubin dynamics. Cutaneous bilirubin and serum bilirubin have been demonstrated to have a high correlation, whether assessed visually, by icterometer, or by TcB devices. It should be noted that 36% of the study patients were outpatients, and TcB underestimation in this subset population resulting from exposure of the skin to high levels of ambient lighting might well be of importance. If true, clinicians should seek alternative anatomic sites unexposed to the same levels of ambient lighting.
Also, 6 of 304 study patients had received phototherapy within 8 to 22 hours of their measurement and the TcB measurements were at skin sites unprotected from lights. As participants of the BiliChek phototherapy clinical trials, we observed that the post-phototherapy interval for unprotected skin sites to reequilibrate to bilirubin levels of an exposed skin site could be 36 to 48 hours. Would omission of these patients alter the results of sensitivity and specificity analysis such that the sensitivity would reach a level of 1.0 (no false-negatives) at a significantly higher cutoff point and yield a specificity that would allow for elimination of many more unnecessary blood tests?
Availability of an accurate point-of-care bilirubin analyzer would facilitate system-based bilirubin screening, avoid unnecessary blood tests, and appeal to clinicians and parents. Obviously, we must be thorough and cautious before we adopt such technologies as a replacement for TSB measurement. By the same token, we must be thorough and cautious before we reject or diminish the utility of a new technology if it offers significant benefits. Thus, it is necessary to put these results into perspective and, importantly, caution against holding new technologies and methodologies to a higher standard than truly exists. We urge the authors and the BiliChek manufacturers to continue analysis of this database to better understand its potential utility in clinical practice.
Vinod K. Bhutani, MD
Lois H. Johnson, MD
Glenn Gourley, MD
Department of Pediatrics
University of Pennsylvania School of Medicine
Philadelphia, PA 19107-6192, USA
Department of Pediatrics
University of Wisconsin Waisman Center
Madison, WI 53705-2280, USA
REFERENCES
- Engle WD, Jackson GL, Sendelbach D, Manning D, Frawley WH. Assessment of a transcutaneous device in the evaluation of neonatal hyperbilirubinemia in a primarily Hispanic population.
Pediatrics.2002; 110
:61
–67
[Abstract/Free Full Text] - Bhutani VK, Gourley G, Kreamer BL, Adler SA, Dalin C, Johnson L. Noninvasive measurement of total serum bilirubin in a multiracial predischarge newborn population to assess the risk of severe hyperbilirubinemia. Pediatrics.2000; 106(2) . Available at: http://www.pediatrics.org/cgi/content/full/106/2/e17
- Bhutani VK, Johnson L, Sivieri EM. Predictive ability of a predischarge hour-specific serum bilirubin for subsequent significant hyperbilirubinemia in healthy term and near-term newborns.
Pediatrics.1999; 103
:6
–14
[Abstract/Free Full Text] - Rubaltelli FF, Gourley GR, Loskamp N, Modi N, Roth-Kleiner M, Sender A, Vert P. Transcutaneous bilirubin measurement: a multicenter evaluation of a new device.
Pediatrics.2001; 107
:1264
–1271
[Abstract/Free Full Text] - American Academy of Pediatrics, Provisional Committee for Quality Improvement and Subcommittee on Hyperbilirubinemia. Practice parameter: management of hyperbilirubinemia in the healthy term newborns.
Pediatrics.1994; 94
:558
–565
[Abstract/Free Full Text]
In Reply.—
We appreciate the comments of Bhutani et al regarding our article1 and the opportunity to reply.
Previous studies have demonstrated a close relationship between the BiliChek (BC) and high-performance liquid chromatography (HPLC) values; however, as noted in the article, relatively few comparisons of the BC with elevated total serum bilirubin (TSB) values have been made. Rather than utilize a method that is not readily available (HPLC), our study compared BC results to the reference point that would be used routinely with this device, ie, the hospital laboratory TSB. We believe that the laboratory at Parkland Memorial Hospital provides a reliable determination of TSB, based on the procedures outlined in the "Methods" section. This belief was supported in a separate analysis comparing 26 Parkland Memorial Hospital TSB determinations with HPLC values obtained on the same samples. In this analysis, 14 of 26 HPLC values were >13 mg/dL, and 25 of 26 were >10 mg/dL. We agree that the difference between TSB values obtained in our laboratory and HPLC values should not be underestimated. As noted in the manuscript, the difference, although small, was highly significant (P < .001), with HPLC values tending to be higher (19 of 26 samples). This tendency toward higher HPLC values compared with results in our laboratory suggests that the BC may actually underestimate TSB to a greater extent than our study suggested.
The values of 10 mg/dL and 15 mg/dL were chosen because of their apparent clinical relevance. We agree that additional analysis based on hour-specific bilirubin data developed primarily by Bhutani et al might be of interest. It should be noted that our study infants were chosen because of clinically significant jaundice that prompted the provider to order a TSB, and we did not approach infants from a screening perspective.2 We viewed the inclusion of outpatients (most seen on the day after discharge) as a strength of the study, because in the era of early discharge, these infants form a large proportion of those requiring evaluation3; from a practical standpoint, the BC is used frequently by practitioners in an outpatient setting.
As suggested by the correspondents, we recalculated sensitivities and specificities for various BC cutoff levels after excluding those infants who had been exposed to phototherapy. The results were virtually identical to those shown in Tables 3 and 4 of the article.
We agree emphatically with Bhutani et al that availability of a noninvasive method for estimating TSB is essential, and we are initiating a study to evaluate a new device4 in our nursery. We agree with Schumacher2 that the BC may be useful in screening large numbers of infants who have mild or no jaundice, while it may be less helpful in diagnosing and following infants with relatively high TSB values.
William D. Engle, MD
Gregory L. Jackson, MD, MBA
Department of Pediatrics
University of Texas Southwestern Medical Center
Dallas, TX 75390-9063, USA
REFERENCES
- Engle WD, Jackson GL, Sendelbach D, Manning D, Frawley WH. Assessment of a transcutaneous device in the evaluation of neonatal hyperbilirubinemia in a primarily Hispanic population. Pediatrics.2002; 110 :61 –67
- Schumacher RE. Transcutaneous bilirubinometry and diagnostic tests: "the right job for the tool."
Pediatrics.2002; 110
:407
–408
[Free Full Text] - Maisels MJ, Newman TB. Jaundice in full-term and near-term babies who leave the hospital within 36 hours. Clin Perinatol.1998; 25 :295 –302[Web of Science][Medline]
- Maisels MJ, Ostrea EM, Cepeda E, et al. Evaluation of the Minolta Model 103 transcutaneous bilirubinometer. PediatRes.2002; 51 :341A
PEDIATRICS (ISSN 1098-4275). ©2003 by the American Academy of Pediatrics
CiteULike 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  H T Ho, T K Ng, K C Tsui, and Y C Lo Evaluation of a new transcutaneous bilirubinometer in Chinese newborns Arch. Dis. Child. Fetal Neonatal Ed., November 1, 2006; 91(6): F434 - F438. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
