Incidental Finding on a Blood Test
What unexpected findings mean, which ones matter, and how Australian GPs decide between watching, investigating and reassuring.
The Quick Answer
An incidental finding is an unexpected abnormal result on a blood test ordered for a different reason. The test was looking at one thing — perhaps a routine check, a pre-op screen, or testing for fatigue — and a totally separate marker came back outside range.
The most common incidental findings in Australian general practice are monoclonal protein (MGUS), mildly raised liver enzymes, raised ferritin, mildly raised calcium, low B12, raised PSA, mild eosinophilia and positive ANA. Some need investigation, some need annual monitoring, and some need nothing at all beyond reassurance.
The decision framework is straightforward: actionable now (refer or treat), actionable monitor (annual review), or no action needed. Your GP works out which category each incidental finding belongs to based on the magnitude, related markers, your symptoms and family history.
Why Incidentals Are So Common
The simple reason is statistics. Reference ranges cover 95% of healthy adults, so on any single marker about 1 in 20 healthy people will fall outside the range purely by chance. With a comprehensive 20-marker panel, the probability of a perfectly healthy adult flagging at least one result is around 64%. Order more markers and more incidentals appear.
The other reason is that many slow-moving conditions are silent. NAFLD, haemochromatosis, MGUS, subclinical hypothyroidism, mild kidney disease, prediabetes, early Sjogren's — all can sit quietly for years before any symptom appears, and they often turn up first as an incidental finding on a panel ordered for something else. This is the upside of incidentals: they catch real disease early.
The downside is that incidentals also generate anxiety and downstream testing for findings that turn out to be benign (so-called VOMITs — Victims of Modern Imaging Technology, with the lab equivalent for blood tests). This is why the Australian framework emphasises stratifying findings carefully rather than chasing every flag.
Common Incidental Findings in Australian General Practice
These are the unexpected findings most often turning up on routine blood panels, grouped by typical action: monitor (annual review), investigate (further tests), or reassure (no further action needed).
Raised ferritin (300-1000 mcg/L)
Most often inflammation, fatty liver, alcohol, or metabolic syndrome. Less often iron overload (haemochromatosis). Check transferrin saturation — over 45-50% suggests true iron overload needing further evaluation.
Monoclonal protein (MGUS)
Found on protein electrophoresis. About 3-4% of adults over 50. About 1% per year progresses to multiple myeloma. Risk-stratified by paraprotein size, type and free light chain ratio. Most need annual monitoring only.
Mildly raised liver enzymes (ALT/AST)
Most often fatty liver (NAFLD) in Australia, affecting 1 in 4 adults. Other causes: alcohol, viral hepatitis, medications, autoimmune. Persistent elevation triggers a full liver screen and usually an ultrasound.
Mild eosinophilia (0.5-1.5)
Allergy, asthma, eczema, drug reactions and parasites are the common causes. Persistent eosinophilia over 1.5 needs further workup including stool studies and sometimes haematology referral for hypereosinophilic syndrome.
Raised ALP (alkaline phosphatase)
GGT helps distinguish liver source (GGT also up) from bone source (GGT normal). Bone causes include Paget disease, fractures, vitamin D deficiency in adults. Liver causes include cholestasis, fatty liver, drug effects.
Positive ANA at low titre
About 10-15% of healthy people have a positive ANA at titre 1:80 or 1:160 with no autoimmune disease. Higher titres (1:640 and above) and specific antibodies (anti-dsDNA, anti-Smith) are more meaningful. Repeat is not usually helpful.
Raised mean platelet volume (MPV)
On its own, a raised MPV is rarely significant. Reflects young platelets in circulation. Only meaningful in the context of low platelets (raised MPV with low platelets suggests platelet destruction rather than production failure).
Raised total protein
Reflects either raised albumin (rare, usually dehydration) or raised globulins. Persistently raised total protein needs serum protein electrophoresis to look for monoclonal paraprotein (myeloma, MGUS) or polyclonal increase (chronic inflammation, liver disease).
Raised IgG (immunoglobulin G)
Polyclonal IgG rise suggests chronic infection, autoimmune disease, liver disease. Monoclonal IgG rise (visible as a single spike on electrophoresis) suggests MGUS or myeloma. Always interpreted together with electrophoresis.
Mildly low B12
Borderline B12 (150-220 pmol/L) may be true deficiency or false-low. Methylmalonic acid (MMA) or active B12 (holotranscobalamin) clarifies. Symptoms (tingling, fatigue, memory) plus borderline B12 usually treated regardless of confirmation.
Slightly raised TSH
Subclinical hypothyroidism (TSH 4-10 with normal T4) affects up to 10% of adults. Most do not need treatment, but trial of thyroxine is offered if symptomatic, pregnant, or thyroid antibodies positive. Annual monitoring otherwise.
How Patients With Incidental Findings Usually Present
The clinical picture around an incidental finding shapes how worried to be. Same lab value, very different stories depending on context.
No symptoms, picked up on routine check
The classic incidental finding scenario. Annual check, screening panel before a procedure, or a test ordered for something unrelated. The result is unexpected and the patient feels well.
Subtle symptoms in retrospect
Sometimes the incidental finding triggers a re-evaluation of mild symptoms the patient had dismissed (mild fatigue, occasional bone pain, vague gut symptoms). The finding makes the symptoms make sense.
Worried about cancer or serious disease
Many people understandably worry that an unexpected lab finding might mean cancer or something serious. Most incidentals are not cancer, but the anxiety is real and deserves a real conversation with the GP.
Family member with similar finding
Family history of haemochromatosis, familial hypercholesterolaemia, autoimmune disease or blood disorders changes how to interpret an incidental finding. Always tell your GP about close relatives with similar lab abnormalities.
Found while screening for something else
Pre-operative bloods reveal anaemia. Insurance medical reveals raised PSA. Pregnancy bloods reveal low platelets. Workplace medical reveals raised liver enzymes. The screening reason and the finding are often unrelated.
Asymptomatic but the lab is well outside range
Very high ferritin (over 1000) or very low haemoglobin in someone who insists they feel fine. The disconnect between the lab and the symptoms makes both the doctor and patient pause. Usually warrants prompt investigation.
Multiple incidentals together
Several unexpected findings on the same panel can paint a picture (raised ferritin + raised ALT + low T4 + raised globulin = systemic inflammation; investigation needed). Cluster matters more than any single incidental.
Repeat confirms the finding
An incidental that persists across two or three blood tests is far more likely to be real than one that resolves on repeat. Persistence rules out lab noise and acute illness as explanations.
Red Flags — Incidental Findings That Need Prompt Action
Most incidentals are not urgent. These are the combinations that warrant prompt investigation rather than wait-and-see:
Monoclonal protein in older adult
Monoclonal protein (paraprotein) found incidentally in an adult over 50, particularly with bone pain, kidney impairment, anaemia or raised calcium, warrants prompt haematology referral. The combination raises concern for multiple myeloma rather than MGUS.
Persistent unexplained ferritin over 1000 mcg/L
Very high ferritin without obvious inflammatory cause warrants prompt investigation for haemochromatosis (especially with raised transferrin saturation), inflammatory disease, liver disease, or rarely macrophage activation syndrome.
Persistent eosinophilia over 1.5
Sustained eosinophil count over 1.5 needs more than a wait-and-see approach. Causes range from parasitic infection through drug reactions to vasculitis and hypereosinophilic syndrome. Sustained levels over 5 are a haematology emergency.
Raised calcium with symptoms
Hypercalcaemia found incidentally, particularly with fatigue, constipation, abdominal pain, bone pain or kidney stones, warrants prompt investigation for primary hyperparathyroidism, malignancy, sarcoidosis or vitamin D toxicity. Calcium over 3.0 mmol/L is urgent.
New onset cytopenia
Unexpected low haemoglobin, low platelets, or low white cells found incidentally needs explanation. Causes range from medication side effect through B12/folate deficiency to bone marrow disease. Multiple cytopenias (pancytopenia) is a haematology referral.
PSA over 10 incidentally
PSA above 10 ng/mL found incidentally usually warrants urology referral and MRI rather than wait-and-see. While benign causes (BPH, prostatitis, recent catheterisation) are possible, the threshold for investigation is lower above 10.
How GPs Work Up an Incidental Finding
Australian GPs follow a fairly standard sequence when faced with an unexpected finding. Knowing the sequence helps you understand why each step is being taken.
Confirm the result on repeat
For most incidental findings the first step is to repeat the test. About 30-50% of one-off incidental findings resolve on repeat — statistical noise, lab artefact, recent illness, or sampling issue. Confirming the finding is real saves a lot of unnecessary downstream investigation.
Look at related markers in context
A raised ferritin alone is hard to interpret. Raised ferritin with raised transferrin saturation suggests iron overload. Raised ferritin with raised CRP suggests inflammation. Raised ferritin with normal everything else is usually idiopathic. Patterns guide next steps.
Take a careful history
Many incidentals are explained by history: medications (statins raising CK, methotrexate raising MCV, PPIs lowering B12), alcohol (raised GGT, ferritin, MCV), supplements (biotin interfering with assays), recent illness (raised CRP, low albumin), pregnancy or hormonal change.
Look for family history
Genetic conditions often present as incidental findings: haemochromatosis (raised ferritin), familial hypercholesterolaemia (high LDL), familial hyperbilirubinaemia (Gilbert syndrome, raised bilirubin), congenital long QT (abnormal ECG). Always ask about close relatives with similar findings.
Categorise the finding
Three buckets: actionable now (refer or treat), actionable monitor (annual review), or no action needed. The category drives the conversation with the patient. Sometimes the right answer is “we will not chase this any further” — and that should be said out loud.
Refer if persisting and unexplained
Persistent incidental findings that cannot be explained by lifestyle, medication or known conditions usually warrant specialist input. MGUS to haematology. Persistently raised liver enzymes to gastroenterology. Persistently raised PSA to urology. Persistent eosinophilia over 1.5 to haematology.
Set the monitoring plan
For findings that do not need treatment but should not be ignored, agree on a monitoring plan. MGUS yearly. Mild persistent eosinophilia 3-6 monthly. Raised ferritin with normal saturation 6-12 monthly. Borderline subclinical hypothyroidism 6-12 monthly. Knowing the plan reduces anxiety and prevents drift.
What Each Common Incidental Finding Usually Needs
MGUS (monoclonal gammopathy)
Annual blood and urine monitoring, usually under haematology guidance. Tests typically include full blood count, calcium, kidney function, protein electrophoresis with immunofixation, free light chains, and urine Bence-Jones protein. Low-risk MGUS may be safely monitored every 1-2 years; higher-risk variants more often.
Raised ferritin
Iron studies (transferrin saturation, iron, TIBC) to distinguish true iron overload from inflammation. Saturation over 45-50% with raised ferritin suggests haemochromatosis — HFE gene test usually offered. Persistent very high ferritin (over 1000) often warrants gastroenterology or haematology referral. Mild rises with metabolic syndrome respond to weight loss.
Mildly raised liver enzymes
Repeat in 4-8 weeks. If persistent: full liver screen (viral hepatitis B and C, autoimmune liver screen, ferritin, iron studies, ceruloplasmin if young, lipids, HbA1c) plus liver ultrasound. NAFLD is the most common diagnosis in Australia and responds to weight loss, exercise and metabolic control.
Raised PSA found incidentally
Repeat in 6-8 weeks with no ejaculation or cycling for 48 hours before the draw and no recent prostate exam, infection or catheterisation. Persistent elevation usually leads to urology referral and increasingly multiparametric MRI of the prostate before any decision about biopsy. Free/total PSA ratio under 25% raises concern for cancer.
Mild eosinophilia
Review medications and allergies. Take a travel history (parasites). Consider stool ova/cysts/parasites if any history of overseas travel or gut symptoms. Repeat in 4-12 weeks. Persistent eosinophilia over 1.5 needs haematology input. Sustained levels over 5 are a haematology emergency for hypereosinophilic syndrome.
Related Reading
SmarterBlood Flags Incidentals and Explains Them
Upload your pathology report and SmarterBlood's AI surfaces every incidental finding, explains what it usually means, and shows what your GP typically does next — in plain English with Australian reference ranges.
This page provides general educational information about incidental findings on Australian blood test reports. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your GP about unexpected results — they have access to your full medical history and can interpret findings in context. SmarterBlood does not provide medical care.