Serum Protein Electrophoresis (SPEP) Test

SPEP normal protein fractions

What is an M-spike?

Abnormal SPEP patterns

Questions to ask your doctor

• Is there an M-spike on my SPEP?
• Do I need immunofixation to identify the type of protein?
• Could this be myeloma or MGUS?
• How often should MGUS be monitored?

SPEP and the tests it is compared with

SPEP is often ordered alongside — or confused with — other protein tests. Each answers a different question:

No single one of these settles the question alone. SPEP finds the pattern, immunofixation names the protein, and free light chains catch what SPEP can miss — which is why doctors usually order them as a set.

Reading your SPEP report: what your doctor actually looks at

An SPEP report is read as a picture, not a number. Here is the checklist a doctor runs through:

1. The shape of the gamma region. A sharp, narrow spike means one clone (monoclonal); a broad, diffuse rise means many clones responding to inflammation or liver disease. The shape decides the entire follow-up.
2. The size of any M-spike. Small incidental bands are often MGUS and monitored; larger bands push the workup toward myeloma. Size is read in g/dL alongside the pattern.
3. Albumin and the other fractions. Low albumin points toward liver disease, kidney protein loss or malnutrition — a separate signal from any spike, and worth chasing on its own.
4. Whether the companion tests were done. Immunofixation, free light chains, calcium, kidney function and a full blood count complete the picture. If your report shows electrophoresis alone, ask whether the rest were ordered.
5. The clinical story behind the order. Unexplained anaemia, kidney problems, bone pain or repeated infections change how the same pattern is read. Make sure the reason for the test is on the request.

If the words “monoclonal protein” appear on your report, the calm next step is characterisation — identifying the protein and its size — not alarm. Discuss the full set of results with your doctor.

SPEP test price in India: typical bands across major lab chains

SPEP is a specialised test, and companion tests such as immunofixation are usually priced separately. Typical list-price bands:

These are approximate bands, not quotes: prices change often and vary by city, and home collection can add a small fee. Where possible, choose a NABL-accredited lab, and remember the reference range printed on your own report is the one that counts.

Frequently Asked Questions

What the test can and cannot settle

Serum protein electrophoresis separates blood proteins by size and charge, producing a pattern rather than a single number. Its main purpose is detecting a monoclonal band, the M-spike, reflecting a single clone of plasma cells producing identical immunoglobulin. What it cannot do is tell you what that clone means. The same finding spans monoclonal gammopathy of undetermined significance, common with age and mostly harmless, through smouldering myeloma, to active myeloma requiring treatment. Distinguishing these needs the clinical picture, blood counts, calcium, kidney function and imaging, not the electrophoresis alone.

Tests usually run alongside it

• Immunofixation, which identifies exactly which heavy and light chain the band contains and is more sensitive for small bands.
• Serum free light chain assay, essential because some myelomas produce light chains only and show no M-spike on standard electrophoresis.
• Urine electrophoresis for Bence Jones protein, historically the classic test for light chain disease.
• Full blood count, calcium, creatinine and albumin, which together identify the organ damage defining active disease.

Reading the other patterns

Not every abnormal electrophoresis involves an M-spike. A diffuse, broad-based increase in the gamma region is polyclonal, reflecting chronic infection, autoimmune disease or liver disease, and is not a marker of malignancy.³ A reduced gamma fraction suggests immune deficiency, whether inherited, drug-induced or secondary to a haematological condition.² Low albumin with raised alpha-2 is the pattern of an acute phase response or nephrotic syndrome. A missing alpha-1 band raises alpha-1 antitrypsin deficiency, worth recognising because it affects both lung and liver.

What follows an incidental M-spike

Most small bands found incidentally in well people prove to be MGUS, which carries a low annual risk of progression and is managed by periodic monitoring rather than treatment. The band size, immunoglobulin type and free light chain ratio together set how closely monitoring is scheduled. Because the finding is common and usually stable, discovering an M-spike is not in itself cause for alarm, but it does need proper characterisation rather than being left unexplained.

MGUS: quantifying the risk of progression

The word "precancerous" is alarming in proportion to the actual risk, which is why numerical framing matters. A landmark long-term follow-up study enrolled 1,384 individuals with MGUS and followed them for a median of 34.7 years; the cumulative probability of progression to multiple myeloma or a related malignancy was approximately 1% per year, translating to roughly 10% at 10 years.¹ Several features predict a higher trajectory: band size above 15 g/L, abnormal serum free light chain ratio, and non-IgG immunoglobulin type each independently increase risk. Low-risk MGUS, small IgG band with normal free light chains, can be rechecked every two to three years, while high-risk patterns warrant annual review with a haematologist. No treatment is offered unless progression to a disorder causing organ damage is confirmed, because the risks of chemotherapy outweigh the benefit at the MGUS stage.

Pharmacist's practical notes

SPEP is a pattern-reading test, which means the shape of the result matters more than any single number. A sharp, narrow spike (an M-spike) points to one clone of plasma cells making identical protein, while a broad, diffuse rise usually reflects general inflammation or liver disease. The two patterns lead to completely different follow-up, so this is a result to read with your doctor rather than interpret alone.

Doctors often order SPEP for clues that do not look like a blood disorder at first glance: unexplained anaemia, kidney problems, bone pain, or repeated infections. If any of these prompted your test, mention them when the blood is drawn so the result is read with the full clinical picture in mind.

A small incidental M-spike can turn out to be MGUS, a premalignant condition that often needs nothing more than periodic monitoring. Finding the words 'monoclonal protein' on a report is frightening, but not every M-spike means myeloma. What matters is the size of the spike, the rest of your results, and your symptoms — all of which a haematologist weighs together.

SPEP is almost always read alongside other tests such as immunofixation, serum free light chains, calcium, kidney function and a full blood count. If your report mentions only the electrophoresis, ask your doctor whether the companion tests were done, because staging and decisions depend on the set, not on SPEP alone.

References

The clinical information on this page is drawn from peer-reviewed sources indexed by the US National Library of Medicine. Links go to the source so you can read it yourself.

1. Kyle RA, Therneau TM, Rajkumar SV, et al. A long-term study of prognosis in monoclonal gammopathy of undetermined significance. N Engl J Med. 2002;346(8):564–569. PMID 11856795 · doi:10.1056/NEJMoa01133202
2. Godelaine J, Gillain C, Lison D, et al. Prevalence of monoclonal proteins in patients with isolated hypogammaglobulinemia on serum protein electrophoresis. Scand J Clin Lab Invest. 2024;84(6):390–395. PMID 39540327 · doi:10.1080/00365513.2024.2429090
3. Hypergammaglobulinemia (Polyclonal Gammopathy). In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK585137