Many routine laboratory tests continue to be used, despite their limited diagnostic or patient management. Newer biomarkers offer more precise and clinically relevant data at similar costs, with greater benefits for clinical decisions.
This overview identifies five outdated tests that clinicians can remove from practice and highlights evidence-based alternatives that improve accuracy and patient outcomes.
Vitamin B12
Total serum vitamin B12 is widely measured but is often unhelpful. Most circulating B12 binds to haptocorrin and is biologically inactive.
Holotranscobalamin is the active form bound to transcobalamin that cells can use and is a more accurate and sensitive marker of B12 status than total serum B12 levels.
It detects early deficiencies more reliably, including in older adults and during pregnancy.Functional markers can aid in diagnosis such as methylmalonic acid or homocysteine. Methylmalonic acid rises when B12-dependent metabolism is impaired. Homocysteine also rises in deficiency, although folate or vitamin B6 deficiency can elevate it as well, which makes it less specific.
Holotranscobalamin measures the active B12 available to tissues, while methylmalonic acid reflects metabolic impairment.
Clinicians may move beyond total B12 levels because holotranscobalamin and methylmalonic acid are better markers of functional B12 status.
Iron Status
Serum iron levels fluctuate widely and do not reflect the availability of iron. A clearer assessment combines ferritin, transferrin saturation, and C-reactive protein (CRP) levels.
Ferritin indicates iron stores but increases with inflammation, which CRP helps interpret. Low ferritin levels with low transferrin saturation confirm absolute deficiency.
High ferritin levels with elevated CRP levels suggest functional deficiency in inflammatory diseases.
Clinicians can omit serum iron levels because ferritin, transferrin saturation, and CRP levels provide a complete picture.
Kidney Function
Creatinine has long been used to assess kidney function; however, its levels vary with muscle mass, age, and sex. A young, athletic adult may show high creatinine levels without kidney impairment, whereas a frail older person may show normal values despite reduced filtration.
Cystatin C provides a clear indication because it is produced at a constant rate by all cells and is minimally influenced by muscle mass.
Evidence shows that cystatin C-based estimates of the glomerular filtration rate detect early kidney damage more reliably and better predict the risk for cardiovascular (CV) events, mortality, and kidney disease.
Clinicians should not rely on creatinine alone, as adding cystatin C provides a more accurate assessment of kidney function.
Testosterone Value
Total testosterone in serum can misrepresent hormone status because most testosterone is bound to sex hormone-binding globulin (SHBG) and is biologically inactive.
Changes in SHBG levels caused by oestrogens, liver disease, or obesity can make total testosterone levels misleading.
The free fraction or free androgen index calculated from testosterone and SHBG provides a more accurate reflection of androgen activity.
Evidence shows that free testosterone or free androgen index improves diagnostic accuracy in men with suspected hypogonadism and women with hyperandrogenism.
Clinicians should not rely on total testosterone levels alone because free or calculated testosterone levels provide a more accurate view of androgen status.
Lipid Profile
Total cholesterol levels provide only a broad indication of CV risk.
Apolipoprotein B, low-density lipoprotein (LDL), and non-high-density lipoprotein (HDL) cholesterol provide clearer guidance. Apolipoprotein B quantifies the number of atherogenic fractions including LDL, very LDL, and intermediate-density lipoprotein.
Evidence shows stronger associations between apolipoprotein B and CV risk than with LDL or total cholesterol.
Elevated apolipoprotein B levels are also correlated with markers of insulin resistance, such as increased fasting glucose levels, and metabolic disorders.
The apolipoprotein B to apolipoprotein AI ratio is considered a predictor of CV risk.
Non-HDL cholesterol is a simple and cost-effective measure that captures all atherogenic fractions and is useful in patients with hypertriglyceridaemia or metabolic syndrome.
Total cholesterol has limited value. Apolipoprotein B and non-HDL cholesterol give clinicians more clinically relevant information about CV risk.
Rethink Routines
Routine diagnostics often follow habits. More specific markers reduce unnecessary testing, detect risk earlier, and improve treatment decisions.
https://www.medscape.com/viewarticle/doctors-5-deceptive-lab-tests-drop-better-options-2025a1000ttn
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