Which biochemical markers are most useful for diagnosing neuroendocrine tumours in primary care?

Chromogranin A (CgA) is the most useful biochemical marker for diagnosing neuroendocrine tumours (NETs) in primary care, as it is a general marker elevated in many NETs and widely used in clinical practice.

24-hour urinary 5-hydroxyindoleacetic acid (5-HIAA) measurement is also valuable, particularly for serotonin-secreting NETs such as carcinoid tumours.

Other markers like neuron-specific enolase (NSE) and pancreastatin may have roles but are less commonly used in primary care due to limited specificity and availability.

UK guidelines do not specifically recommend routine biochemical marker testing for NETs in primary care but emphasize symptom-directed investigations and referral for imaging and specialist assessment when NET is suspected ¹.

Recent literature supports the use of CgA as a sensitive, though not entirely specific, marker for NET diagnosis and monitoring, highlighting its prognostic and predictive value (Chan et al., 2017; Herrera-Martínez et al., 2019).

However, clinicians should be aware of factors that can falsely elevate CgA, such as proton pump inhibitor use and renal impairment, which may limit its specificity (Konukiewitz et al., 2022).

In summary, while primary care biochemical testing for NETs is not routinely outlined in UK guidelines, Chromogranin A and 24-hour urinary 5-HIAA are the most useful markers when NET is suspected, with specialist referral recommended for further diagnostic workup ¹ (Chan et al., 2017; Herrera-Martínez et al., 2019; Konukiewitz et al., 2022).