Low-cost, portable icterometer useful for visual jaundice assessment in babies

Jairia Dela Cruz
08 May 2019
Low-cost, portable icterometer useful for visual jaundice assessment in babies

Bili-ruler, a simple, low-cost icterometer, may help improve the objectivity of visual examination for hyperbilirubinemia in neonates, with a recent study showing that the device can accurately identify different clinically relevant thresholds of the condition.

“Icterometry is an indirect visual measure of the transcutaneous degree of jaundice, indicating bilirubin concentrations in subcutaneous tissue and fat,” researchers said.

The current device builds upon the original handheld Gosset icterometer developed in the 1950s. While the latter used five shades of yellow made from robbialac paint, Bili-ruler features six swatches that are digitally standardized and calibrated, arranged according to increasing hues.

Bili-ruler also simplifies colour matching by integrating a clear, circular window within each swatch through which the assessor visualizes the hue of the underlying subcutaneous tissue of the infant examined and makes a relatively simpler binary (yes or no) matching decision. This process is repeated for each colour on the ruler, and the assessor chooses the Bili-ruler score (1–6) that most closely matches the underlying skin colour.

Researchers tested Bili-ruler on 790 infants from the US and Bangladesh. The measurements were performed on the forehead, nose, abdomen, palms and soles of the infant and evaluated against standard transcutaneous bilirubin (TcB) and total serum bilirubin (TSB) concentrations.

Bili-ruler scores on the nose correlated with TcB and TSB levels (r=0.76 and r=0.78, respectively), accurately distinguishing different clinical thresholds of hyperbilirubinemia, as defined by TcB. For example, a score of 4 had 94.1 percent sensitivity and 85.0 percent specificity for identifying a TcB ≥17 mg/dL. [Pediatrics 2019;doi:10.1542/peds.2018-2039]

Areas under the receiver operating characteristic curve for identifying TcB ≥11, ≥13 and ≥15 mg/dL were 0.92, 0.93, and 0.94, respectively, and 0.90, 0.87, and 0.86 for identifying TSB ≥11, ≥13 and ≥15 mg/dL. Interrater agreement was high, with 97 percent of scores by independent readers falling within 1 score of one another (n=88).

“Th[e] low-cost, portable and accurate tool may be used to improve the identification of hyperbilirubinemia in settings where laboratory testing and/or electronic transcutaneous devices are unavailable, and thus help to guide appropriate referral and case management,” researchers said. “This is the first step required to help reduce mortality and morbidity related to hyperbilirubinemia in the hardest-to-reach communities.

“Validity in varying ethnicities and skin tones is an important consideration for the use of icterometry in different populations. In our study, mean bilirubin levels for each icterometer score were relatively similar between various ethnic groups [ie, White and South Asian], with mean bilirubin within 2-mg/dL for Bili-ruler scores with adequate sample size,” they noted. "A larger validation study in African neonates is needed and currently being planned."

Finally, researchers pointed out the need to understand potential barriers to uptake and scale, given that icterometers were previously available and considered valid.

“It is unclear whether the high cost or low availability of devices were reasons for low uptake in low-to-middle income countries. Previous icterometers cost $15 per device in the 1950s, equating to $50 today with inflation. The Bili-ruler currently costs $5 per device; however, at scale, the ruler would cost <$1 per device to produce, which could improve potential for scalability,” they said.

“The current price point assumes materials cost at relatively low-volume production. We are exploring alternative manufacturing methods to support a more robust version that is suitable for large-scale production,” they added.

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