When should liver function tests (LFTs) be repeated in a patient with infectious mononucleosis (mono) and elevated liver enzymes?

Repeat Liver Enzyme Testing in Infectious Mononucleosis

Serial liver function test monitoring is not required in immunocompetent patients with infectious mononucleosis who have subclinical liver enzyme elevations. 1, 2

Initial Assessment

• Check baseline liver enzymes at presentation if clinically indicated, as 57-80% of infectious mononucleosis patients will have abnormal transaminases (ALT elevated in 62%, AST in 57%) 1, 2
• The presence of elevated liver enzymes increases clinical suspicion for infectious mononucleosis when the heterophile antibody test is negative 3
• Bilirubin elevation occurs in only 16-40% of cases, with clinical jaundice in approximately 17% 1, 4

Follow-Up Monitoring Strategy

For immunocompetent patients with subclinical liver enzyme elevation:

• No routine serial monitoring is necessary - the evidence strongly supports that repeat testing following initial abnormalities is not required 1, 2
• Liver enzymes typically normalize within 6-12 weeks (median 32 days, interquartile range 20-50 days), though resolution can take up to 6-10 months in some cases 1, 2, 4
• Maximum abnormalities occur between weeks 2-4 of illness, with normalization usually by week 6 4

Repeat testing is only indicated if:

• Symptoms develop suggesting hepatic dysfunction: jaundice, right upper quadrant pain, severe fatigue, dark urine, pruritus, or unexplained clinical deterioration 5
• The patient is immunosuppressed (higher risk of severe disease and significant morbidity) 3
• Initial presentation includes clinical jaundice or other red flags requiring immediate referral 5

Imaging Considerations

• Routine abdominal ultrasound is not required to evaluate liver enzyme derangement in infectious mononucleosis 1, 2
• No cases of decompensated liver disease or chronic hepatitis have been reported in immunocompetent patients with infectious mononucleosis-related transaminitis 1, 4

Common Pitfalls to Avoid

• Do not simply repeat the same liver enzyme panel without clinical indication - this is inefficient, delays appropriate management, and causes unnecessary patient anxiety 5
• The magnitude of liver enzyme elevation does not correlate with prognosis or need for monitoring in infectious mononucleosis 5
• Avoid assuming that elevated enzymes require serial monitoring "until normal" - the natural history shows spontaneous resolution without intervention 1, 2