From the Guidelines
Scleral icterus becomes apparent when serum bilirubin levels are above 3 mg/dl. This is based on the most recent and highest quality study available, which discusses the natural history of HBV reactivation and its effects on liver function, including the progression to acute liver failure 1. According to this study, after rapid HBV replication and increase in serum ALT, the bilirubin starts increasing, and once it is above 3 mg/dl, scleral icterus becomes apparent.
Some key points to consider when evaluating scleral icterus include:
- The yellowing of the whites of the eyes is one of the earliest visible manifestations of hyperbilirubinemia and jaundice
- The detection of scleral icterus can vary based on lighting conditions, observer experience, and patient factors such as skin tone
- In some individuals, especially those with darker skin pigmentation, scleral icterus may be the most reliable external sign of hyperbilirubinemia
It's worth noting that the study by 1 provides valuable insights into the progression of HBV reactivation and its effects on liver function, including the development of scleral icterus. The study highlights the importance of monitoring liver function and bilirubin levels in patients at risk of HBV reactivation, as early detection and treatment can significantly improve outcomes.
The clinical significance of scleral icterus cannot be overstated, as it is often a sign of underlying liver dysfunction or disease. As such, it is crucial to investigate the underlying cause of scleral icterus and to monitor liver function closely. By doing so, healthcare providers can provide timely and effective treatment, reducing the risk of morbidity and mortality associated with liver disease.
From the Research
Scleral Icterus and Serum Bilirubin
- Scleral icterus is a clinical sign that can be detected when serum bilirubin levels are elevated, but the exact threshold is not precisely defined in the provided studies 2, 3, 4, 5, 6.
- A study published in 1997 found that at a total serum bilirubin of 42.8 mmol/l (2.5 mg/dl) and 53.0 mmol/l (3.1 mg/dl), 58% and 68% of examiners detected the presence of scleral icterus, respectively 5.
- The same study noted that even at a serum bilirubin level of 42.8 mmol/l (2.5 mg/dl), approximately one-third of medical examiners did not detect scleral icterus, suggesting that the relationship between serum bilirubin and scleral icterus detection is not straightforward 5.
- Other studies discuss the measurement and clinical usefulness of bilirubin in liver disease 4, as well as the development of sensors for point-of-care measurement of bilirubin 6, but do not provide a specific serum bilirubin threshold for scleral icterus.
Detection of Scleral Icterus
- The detection of scleral icterus can be influenced by the level of training of the examiner, with medical students being more likely to produce false-positive results 5.
- The study published in 1997 found that level of training did not appear to influence sensitivity, as false-negatives were not attributable to medical students alone 5.
- The presence of scleral icterus can be an important clinical sign in the diagnosis of various conditions, including Gilbert syndrome 2 and syphilitic hepatitis 3.