High bilirubin

Acceptability at Recruitment

ACCEPTABLE

Acceptability at CT / Work-Up

ACCEPTABLE

Individual at Risk

DONOR/RECIPIENT

Explanation of Condition

High bilirubin can have a number of different causes, some of which are benign and acceptable for donation, and some of which indicate an underlying disease process which can put both the recipient and donor at risk.

Bilirubin is a byproduct in the breakdown of red blood cells. Red bloods cells (which carry oxygen around the body) have a lifespan of around 120 days. Once they reach the end of their lifespan, they are broken down. A byproduct of haemoglobin breakdown is bilirubin.

Bilirubin exists in three forms:

- Unconjugated bilirubin

- Albumin-bound bilirubin (which is also unconjugated)

- Conjugated bilirubin

Blood tests usually differentiate between the types of bilirubin, but sometimes only a "total bilirubin" result may be available initially.

Bilirubin initially circulates in the body as unconjugated bilirubin. In this form, it is bound to albumin which acts as its vehicle to transport it around the body.

Unconjugated bilirubin arrives at the liver where it is processed into conjugated bilirubin.

Conjugated bilirubin is excreted through the bile ducts into the bowel where it is excreted in stool. Conjugated bilirubin is also excreted through urine. It is bilirubin that gives urine and faeces their colours.

High bilirubin can happen at different stages. If the red blood cells are defective and are therefore not living as long as they should, unconjugated bilirubin levels increase (due to increased turnover of the red blood cells).

In addition, some conditions result in the liver being slower than usual at processing bilirubin. One such condition is Gilbert's Syndrome, which is a recessively-inherited genetic disorder in which the UDP-1 enzyme is deficient. In Gilbert's Syndrome, unconjugated bilirubin levels increase in times of physiological stress (e.g. infection, dehydration) up to 3x the normal level. Gilbert's Syndrome is entirely harmless and is not an exclusion to donating. It is suspected that around 1 in 20 people in the UK have Gilbert's Syndrome, and often will not be aware until it is incidentally picked up on a blood test.

Other genetic disorders also affect the liver's ability to process bilirubin, but in these cases bilriubin can become dangerously elevated (e.g. Crigler-Najjar Syndrome, Rotor Syndrome).

If there is a blockage in the bile ducts (e.g. due to gallstones or a tumour), bilirubin levels can also build up. In these situations, the elevated bilirubin is conjugated in nature (as it becomes blocked after being processed by the liver).

Guidance

If bilirubin levels are <30umol/L, Gilbert's syndrome can be diagnosed if the FBC and LFTs are normal without the need for a split bilirubin test.

If bilirubin levels are <30umol/L and the FBC is abnormal, this can suggest an inherited or haemolytic anaemia, and appropriate work-up should be undertaken for this possibility. If such a diagnosis is made, see the relevant page for details on whether the donation can proceed (some types of anaemia are an exclusion).

If bilirubin is >30umol/L but <3x the upper limit of normal, diagnose Gilbert’s syndrome if the FBC and LFTs are normal AND the unconjugated bilirubin is ≥70% of the total bilirubin.

If unconjugated bilirubin is <70% of the total, but the LFTs are normal, this should be a case-by-case discussion with a senior medical officer or donor consultant.

If bilirubin levels are elevated in any capacity and associated with abnormal LFTs, the donation should be stopped and the donor should be referred to Hepatology on an urgent basis via their GP.

Version

Version 1, Edition 1

Date of Last Update

23rd May 2024