Calprotectin vs Lactoferrin: Choosing a Stool Test

Klein, Thomas; Weber, Hans; Mitchell, Sarah

Which stool marker should you choose first?

Fecal calprotectin is usually the first-choice stool inflammation marker because it is widely available, quantitative, and has the strongest role in separating likely inflammatory bowel disease from functional bowel symptoms. 糞便ラクトフェリン検査 results are a sensible alternative when that is the locally validated assay, but ordering both at the outset rarely changes care.

For a person with 6 weeks of loose stools, cramping, and no weight loss or rectal bleeding, I would generally begin with calprotectin plus targeted infection testing rather than colonoscopy. A result below 50 µg/g makes significant colonic inflammation less likely, while a clearly elevated result provides a reason to look further. The AGA guideline for chronic watery diarrhoea supports calprotectin or lactoferrin as screening tests for inflammatory conditions (Smalley et al., 2019).

Choose lactoferrin when your gastroenterology service uses it consistently, when the laboratory reports a validated quantitative value, or when it is bundled with an infectious diarrhoea work-up. Do not choose it because it sounds more specific: both proteins are released when neutrophils enter the bowel lumen. The practical issue is whether your clinician can compare the result with your prior samples using the same assay.

カンテスティは AI血液検査分析装置 that places related results such as hemoglobin, CRP, albumin and iron indices alongside a stool-marker report; it does not replace the stool assay or a clinician’s diagnosis. If fatigue accompanies diarrhoea, a blood test for diarrhoea can help identify dehydration, anemia, or electrolyte loss that changes urgency.

A useful rule of thumb

Use one validated marker first, repeat the same marker when a result is borderline or when monitoring treatment, and reserve dual testing for a specific gastroenterology question. Changing assay halfway through follow-up creates apparent trends that may be laboratory noise rather than biology.

What fecal calprotectin actually detects

Calprotectin measures a calcium- and zinc-binding protein released predominantly from neutrophils in the intestinal tract. A higher stool concentration reflects neutrophil migration into the gut, which is common in active IBD but also occurs with several non-IBD conditions.

Calprotectin is the S100A8/S100A9 protein complex, and it remains relatively stable in stool for several days at room temperature—one reason it works well as a home collection test. Its biological strength is locality: unlike CRP, it reflects cellular activity in the intestinal lumen rather than a whole-body acute-phase response. A normal CRP therefore does not cancel a high calprotectin result.

In adult practice, laboratories commonly classify less than 50 µg/g as normal and more than 150–250 µg/g as increasingly compatible with active intestinal inflammation. These are decision thresholds, not universal biological borders. Some European services use 100 µg/g as the referral threshold, while pediatric and assay-specific reference intervals can differ substantially.

I have seen a 28-year-old with a calprotectin of 680 µg/g, a normal CRP, and ultimately ulcerative colitis limited to the rectum and sigmoid colon. That pattern is not unusual: local mucosal inflammation can be active without a strong systemic signal. Our fecal calprotectin range guide explains why the laboratory’s own method and units should stay attached to every result.

What fecal lactoferrin detects differently

Lactoferrin detects another neutrophil-derived protein and answers nearly the same biological question as calprotectin: is there active intestinal neutrophil inflammation? It does not identify ulcerative colitis, Crohn’s disease, bacterial colitis, or another cause on its own.

Lactoferrin is an iron-binding glycoprotein stored in neutrophil secondary granules and released during activation. A positive qualitative fecal lactoferrin test is useful because it argues against uncomplicated IBS in the right clinical setting. Quantitative assays vary: one commonly used method defines a negative value as less than 7.25 µg/g, so never apply a calprotectin cutoff to a lactoferrin report.

The evidence does not show that lactoferrin is categorically superior. In a diagnostic meta-analysis, Wang and colleagues found fecal lactoferrin had pooled sensitivity of 82% and specificity of 95% for distinguishing IBD from non-IBD controls, although accuracy estimates shift with disease prevalence and study design (Wang et al., 2015). That impressive specificity still does not convert a positive result into an IBD diagnosis.

A positive lactoferrin result is especially worth discussing when diarrhoea began abruptly after travel, antibiotics, contaminated food exposure, or contact with someone unwell. In those situations, clinicians usually add pathogen testing rather than jumping straight to an IBD label. Our guide to 便培養の結果 covers what a negative or mixed-growth report can and cannot settle.

How to read cutoffs without overreacting

A calprotectin value below 50 µg/g is usually normal for adults, 50–150 µg/g is often an indeterminate zone, and values above 250 µg/g raise concern for active inflammation. Lactoferrin uses assay-specific cutoffs, commonly a qualitative positive or a quantitative threshold near 7.25 µg/g.

The 50 µg/g calprotectin threshold is designed for sensitivity: it catches most clinically significant inflammatory disease at the cost of some false positives. The 250 µg/g threshold is more useful for specificity and for monitoring established IBD. Between them lies the frustrating middle, where medication exposure, recent gastroenteritis, age, and trajectory matter more than a single number.

A change from 72 to 94 µg/g is often less meaningful than a change from 85 to 430 µg/g, particularly if both samples were tested by the same laboratory. Stool consistency can influence extraction and biological variation is real. Dr. Thomas Klein’s practical advice is to record NSAID use, recent infection, menstrual contamination, and collection date before interpreting a modest rise.

For a disciplined approach to serial values, compare the sample date with symptoms and related labs rather than treating every flagged result as disease progression. Our 血液検査トレンドガイドでパターンを見てください explains the same principle of reference change and analytic variation in laboratory medicine.

たいてい安心材料 <50 µg/g calprotectin Active colonic IBD is less likely in adults without alarm symptoms.

境界域 50–150 µg/g calprotectin Review NSAIDs, infection and symptoms; repeat testing is often appropriate.

明らかに上昇 150–250 µg/g calprotectin Persistent elevation warrants clinical assessment and often further investigation.

著しく高い >250 µg/g calprotectin Suggests active mucosal inflammation but still requires cause-specific evaluation.

Why both markers can be high without IBD

Elevated stool inflammation markers occur with enteric infection, NSAID exposure, diverticulitis, colorectal neoplasia, microscopic colitis and IBD. The result confirms an inflammatory signal; it does not disclose the cause, location, duration, or severity by itself.

Non-steroidal anti-inflammatory drugs can raise fecal calprotectin, sometimes substantially, by increasing intestinal permeability and causing small mucosal injuries. Ibuprofen, naproxen and diclofenac matter; a clinician may suggest withholding them if medically safe before repeating the test. Do not stop prescribed aspirin, anticoagulants, or pain medicines without asking the prescriber first.

Acute bacterial gastroenteritis may produce calprotectin values above 500 µg/g and a positive lactoferrin, which is why a stool pathogen panel can be more informative than an urgent colonoscopy in the first days of illness. Conversely, giardiasis may cause prolonged diarrhoea with less striking neutrophilic marker elevation. The symptom timeline often carries more diagnostic weight than patients expect.

カンテスティは AIラボ検査解釈サービス that can flag an inflammation pattern such as low hemoglobin, low albumin, thrombocytosis and raised CRP for clinician review, but those blood findings do not prove the source is intestinal. For people with blood in the stool, FIT follow-up and colonoscopy timing is a separate issue from calprotectin and should not be delayed.

When a normal result can still miss disease

Normal calprotectin or lactoferrin makes active colonic inflammation less likely, but it cannot fully exclude Crohn’s disease, particularly mild or isolated small-bowel disease. A normal result also does not explain persistent weight loss, iron-deficiency anemia, nocturnal diarrhoea, or recurrent visible bleeding.

Small-bowel Crohn’s disease can shed less neutrophil protein into a stool sample than extensive colitis, especially when lesions are proximal or mild. This is one reason symptoms and alarm features overrule a reassuring number. The ECCO-ESGAR diagnostic guideline recommends integrating biomarkers with ileocolonoscopy and cross-sectional imaging when IBD remains clinically suspected (Maaser et al., 2019).

A 46-year-old with calprotectin of 38 µg/g, ferritin of 7 ng/mL, and progressive fatigue deserves evaluation for gastrointestinal blood loss or malabsorption even if bowel frequency is normal. In my experience, the combination of iron deficiency and unexplained symptoms is much more consequential than a single low stool marker. Read our low ferritin and gut clues for the usual next laboratory questions.

Celiac disease, bile acid diarrhoea, pancreatic insufficiency and many medication effects may cause symptoms with normal stool inflammation markers. A normal test is therefore a fork in the road toward non-inflammatory diagnoses, not a declaration that symptoms are psychological or unimportant.

What to do with a borderline calprotectin result

A borderline fecal calprotectin result of 50–150 µg/g is commonly repeated after 2–6 weeks if symptoms are stable and there are no alarm features. The repeat should use the same laboratory method and should be timed away from a recent gastrointestinal infection where possible.

Before retesting, clinicians review NSAIDs, proton-pump inhibitors, antibiotics, acute infections, strenuous endurance exercise and age-related risk. There is no universally agreed washout interval for every medicine. A pragmatic plan is often 2 weeks after an acute illness has settled, provided symptoms do not signal a need for earlier care.

If the repeat falls from 118 to 32 µg/g and symptoms settle, invasive testing may be avoidable. If it rises from 96 to 310 µg/g, the direction adds useful evidence even before an endoscopy result arrives. This is why a single borderline value should rarely trigger panic—or false reassurance.

私たちの borderline calprotectin follow-up guide lays out the questions to bring to a primary-care or gastroenterology appointment. A short symptom diary with stool frequency, nighttime waking, fever and medication dates is usually more useful than obsessively checking food triggers.

How clinicians use markers after IBD is diagnosed

In established IBD, calprotectin is most useful for tracking objective intestinal inflammation and helping decide whether symptoms represent a flare, infection, IBS overlap, or treatment failure. Lactoferrin can also follow activity, but calprotectin has more guideline-supported thresholds for treat-to-target monitoring.

Symptoms and mucosal activity frequently diverge. A patient with ulcerative colitis may feel well while calprotectin climbs from 80 to 360 µg/g, or have urgent bowel motions from bile acid malabsorption while calprotectin remains 28 µg/g. The 2023 AGA ulcerative colitis biomarker guideline advises combining symptoms with biomarkers rather than relying on either alone (Singh et al., 2023).

For remission monitoring, many clinicians view less than 150 µg/g as reassuring, while more than 150 µg/g may warrant repeat testing, endoscopy, or treatment review depending on symptoms and prior disease behaviour. In active symptomatic ulcerative colitis, more than 250 µg/g supports ongoing inflammation. Cutoffs are guides, not instructions to alter biologic treatment without specialist input.

Kantesti AIは、 AIバイオマーカー解釈プラットフォーム that organizes blood-test trends around a patient’s reported treatment dates; it cannot assess stool endoscopic severity from a number alone. Patients taking biologics should also understand which blood safety tests monitor treatment and which symptoms require prompt contact with their IBD team.

How collection errors and timing affect results

Collection quality affects stool marker interpretation because a contaminated, delayed, or poorly sampled specimen can be rejected or produce a less reliable measurement. Most laboratories want a small stool portion placed into the supplied sterile container without toilet water or urine.

Loose stool is usually acceptable for calprotectin and lactoferrin testing; do not wait for a formed sample if diarrhoea is the clinical problem. Avoid collecting from toilet water, and tell the laboratory if the sample includes visible menstrual blood. Storage instructions vary by kit, but many allow short room-temperature transport because calprotectin is comparatively stable.

Sampling a day after a marathon, a bout of gastroenteritis, or colonoscopy bowel preparation may answer the wrong question. Endurance exercise can transiently increase gut permeability and provoke gastrointestinal symptoms. If you are an endurance athlete without red flags, consider timing collection away from a major event; our 持久系アスリートの検査ガイド explains why context changes test interpretation.

The thing is, a perfect collection does not make a nonspecific biomarker specific. A high-quality sample improves confidence in the measurement; it cannot replace the clinical history, examination, and differential diagnosis.

Which blood tests make a stool marker more useful

A CBC, CRP, ferritin, albumin, kidney function and celiac serology often add more clinical value to a raised stool marker than ordering a second stool inflammation protein. The concerning pattern is not any one abnormality but several results that point toward inflammation, malabsorption, or blood loss.

Low hemoglobin, ferritin below 15 ng/mL, albumin below the laboratory reference range, raised platelets, or raised CRP can strengthen concern for clinically meaningful bowel disease. None is diagnostic of IBD. In fact, CRP may remain normal in mild ulcerative colitis, and ferritin can look falsely normal when inflammation raises it as an acute-phase protein.

カンテスティは AI搭載の血液検査解析ツール that reads a CBC, iron studies and CRP in the same clinical frame, including whether a changing hemoglobin level might justify earlier review. Dr. Thomas Klein routinely cautions that an isolated CRP of 12 mg/L is nonspecific, whereas CRP 12 mg/L plus falling albumin and a calprotectin of 740 µg/g is a much more actionable cluster.

For patients whose iron values seem contradictory, our iron studies research guide explains transferrin saturation and ferritin during inflammation. A CBC result guide can also help you identify whether anemia is microcytic, inflammatory, or mixed.

When ordering both tests may be reasonable

Ordering calprotectin and lactoferrin together is usually unnecessary, but it can be reasonable when a specialist is reconciling discordant symptoms, a prior assay cannot be repeated, or a local pathway requires confirmation. Concordant results modestly increase confidence in an inflammatory signal; discordant results usually trigger review, not arithmetic averaging.

A high calprotectin with negative lactoferrin may reflect assay timing, a result near the cutoff, specimen heterogeneity, or analytical differences. A low calprotectin with positive lactoferrin deserves the same disciplined response: verify collection, review the exact assay, check symptoms and test for infection when appropriate. Neither combination has a validated shortcut to diagnosis.

Dual testing can also be useful in research settings where a protocol prespecifies both biomarkers. That is different from routine patient care, where duplicate testing can add cost without improving decisions. Ask the ordering clinician a simple question: “What will we do differently if the second test is positive?”

If a report looks internally inconsistent, use our 定性検査と定量検査のガイド to understand why “positive” and “high” are not interchangeable laboratory statements. Consistency of method matters more than collecting every available marker.

What actually confirms or excludes IBD

IBD is diagnosed through a synthesis of symptoms, ileocolonoscopy with tissue sampling, histology, laboratory tests, and sometimes MRI or CT enterography—not from calprotectin or lactoferrin alone. Stool markers help decide who needs these investigations and whether inflammation may be changing over time.

Colonoscopy allows direct assessment of the terminal ileum and colon and permits tissue examination for chronic inflammatory features, infection, microscopic colitis, dysplasia, and other causes. Imaging is particularly valuable when Crohn’s disease may involve small bowel beyond the reach of a standard colonoscopy. A stool marker is a triage signal, not a microscopic diagnosis.

Do not confuse a fecal immunochemical test with either inflammatory marker. FIT detects human hemoglobin and is used primarily in colorectal cancer screening or lower-GI bleeding pathways, whereas calprotectin and lactoferrin detect neutrophil products. Our comparison of FIT and FOBT explains why a negative inflammation marker does not substitute for recommended cancer screening.

As of September 4, 2026, no major gastroenterology guideline recommends diagnosing Crohn’s disease or ulcerative colitis from a single stool biomarker threshold. That restraint protects patients from both missed disease and unnecessary lifelong diagnostic labels.

Symptoms that outweigh any stool test result

Persistent visible rectal bleeding, black tarry stool, severe abdominal pain, fever, fainting, dehydration, rapidly worsening weakness, or unintended weight loss need timely medical assessment regardless of calprotectin or lactoferrin. A normal result should never be used to wait out a potentially urgent symptom pattern.

The urgent concern is physiology, not the label on a laboratory report. Frequent watery diarrhoea can produce low potassium, acute kidney injury, and orthostatic symptoms before an inflammation marker returns. Adults with inability to keep fluids down, confusion, fainting, or minimal urine output should seek urgent care.

New bowel symptoms after age 50, a strong family history of colorectal cancer, and iron-deficiency anemia alter the threshold for colon evaluation even when calprotectin is low. A stool marker does not assess cancer risk comprehensively. Our mucus in stool red-flag guide distinguishes common benign patterns from symptoms that need examination.

Children, pregnant people, older adults, and people using immune-suppressing medicines need individualized triage because their baseline risks differ. If you are unsure whether symptoms are urgent, contacting a local clinician or urgent-care service is safer than trying to interpret a number in isolation.

A practical conversation to have after your result

The most useful follow-up question is: “Does this result change my need for infection testing, repeat testing, imaging, or endoscopy?” Bringing the exact value, assay name, symptom timeline, medicines, and previous results makes that conversation faster and more clinically precise.

Bring a list of the previous 14 days: stool frequency, overnight symptoms, fever, weight change, travel, antibiotics, NSAIDs, and family history. A calprotectin of 180 µg/g after a 3-day febrile diarrhoeal illness calls for a different plan than the same result after 4 months of nocturnal diarrhoea and weight loss.

Kantesti AI can help you organize accompanying blood reports before an appointment, but diagnosis and treatment decisions belong with the clinician who can examine you and arrange definitive testing. Our 医学的なバリデーションのアプローチ explains how clinical oversight and source checking are built into responsible laboratory interpretation.

For complex cases, ask who will own the follow-up and when you should expect a repeat result or referral decision. The clinicians on our 医療諮問委員会 emphasize that a documented plan beats a vague instruction to “recheck later,” especially when inflammation markers and anemia move in the same direction.

The decision-focused bottom line

Choose calprotectin first in most settings, use lactoferrin when it is your service’s validated alternative, and do not assume either result diagnoses IBD. A low result shifts attention toward functional and non-inflammatory causes, while a persistently high result identifies people who may need infection testing, specialist review, or endoscopy.

For uncomplicated chronic diarrhoea, one normal marker—calprotectin below 50 µg/g or a negative lactoferrin according to that laboratory—can reduce the likelihood of active inflammatory disease. For a value above 250 µg/g or a positive lactoferrin with persistent symptoms, the next question is cause, not certainty. Infection, medicine exposure, IBD, and other inflammatory conditions remain on the list.

Most patients find the ambiguity hardest in the 50–150 µg/g calprotectin zone. In my experience, the best next step is usually a carefully timed repeat, not a dietary cleanse, self-directed steroid use, or an internet diagnosis. Keep the same laboratory where feasible so the trend is interpretable.

Kantestiの AIテクノロジーガイド describes how our systems preserve laboratory context while highlighting questions for medical review. The safe use of any AI interpretation is the same here: use it to prepare for a better clinical conversation, never to override red flags or replace diagnostic care.

よくある質問

カルプロテクチンはIBD検出においてラクトフェリンより優れていますか？

カルプロテクチンは、定量検査として広く利用可能であり、50 µg/g 未満および 250 µg/g 超といった一般的に使用されるモニタリング閾値があるため、IBD が疑われる場合に通常好まれます。ラクトフェリンも有用な好中球由来の便マーカーであり、臨床検査室がバリデートされたアッセイを使用している場合は良好な結果が得られます。感染症、NSAIDs、憩室炎、その他の腸疾患が両者を上昇させる可能性があるため、いずれのマーカーも IBD を確定するものではありません。より良い検査は通常、症状と合わせて主治医が解釈でき、同じ臨床検査方法で繰り返し測定できるものです。.

どのくらいのカルプロテクチン値が懸念されますか？

症状が重篤でない成人において、便中カルプロテクチン値が 50 µg/g 未満であれば、一般的に安心できる値ですが、50–150 µg/g はしばしば境界域とみなされ、2〜6週間後に再検することがあります。150–250 µg/g を超える値は腸管の炎症の可能性が高く、250 µg/g を超える値は、臨床的評価やさらなる検査を促すことが一般的です。正確な対応は、測定法、症状、年齢、NSAIDの使用、および値が上昇しているかどうかによって異なります。細菌性腸炎発症後の 600 µg/g の値は、数ヶ月にわたる慢性の症状中の 600 µg/g とは異なる意味を持つことがあります。.

IBSは高カルプロテクチンまたはラクトフェリンを引き起こす可能性がありますか？

複雑でないIBSは、IBSが好中球を介した腸管炎症を引き起こさないため、通常、便中カルプロテクチンまたはラクトフェリンの上昇を引き起こしません。50〜150 µg/gの軽度のカルプロテクチン上昇は、最近の感染、NSAIDの使用、加齢に関連する要因、またはアッセイのばらつきから生じる可能性があり、IBSを自動的に除外するものではありません。250 µg/gを超える陽性のラクトフェリンまたはカルプロテクチンは、IBSを仮定するのではなく、炎症性または感染性の原因の評価を促すべきです。IBSとIBDは共存する可能性があり、これも症状と傾向が重要である別の理由です。.

Can a normal calprotectin rule out Crohn's disease?

カルプロテクチン値が正常であっても、活動性の腸管炎症性疾患（IBD）の可能性は低くなりますが、クローン病、特に軽症または小腸に限定したクローン病を完全に除外することはできません。50 µg/g 未満の値であっても、鉄欠乏性貧血、体重減少、夜間下痢、持続的な出血、または強い家族歴などの警告所見を覆すべきではありません。臨床医は、臨床的な疑いが依然として高い場合、回盲部大腸内視鏡検査、MR enterography、またはカプセル内視鏡検査を使用することがあります。この結果は、最終的な除外検査としてではなく、確率を調整する証拠の一つとして扱うのが最善です。.

境界域のカルプロテクチン値が検出された場合、再検査すべきですか？

50–150 µg/gという境界域のカルプロテクチン値は、症状が安定し、アラーム症状がない場合に、2〜6週間後に再検することがよくあります。再検する前に、臨床医は最近の胃腸炎、NSAIDの使用、抗生物質の使用、および検体採取条件を一般的に確認します。なぜなら、それぞれが値に影響を与える可能性があるからです。可能な限り同じ検査室アッセイを使用してください。異なる方法からの結果は直接比較できない可能性があるためです。250 µg/gに近づく、またはそれを超える上昇傾向の結果は、一般的に、安定した軽度の高値よりも臨床的な重みがあります。.

Can antibiotics affect fecal calprotectin and lactoferrin?

Antibiotics can affect stool inflammation markers indirectly by treating, triggering, or coinciding with infectious diarrhoea and by altering the intestinal microbiome. A person with antibiotic-associated diarrhoea should be assessed for causes such as Clostridioides difficile rather than interpreting a raised calprotectin or positive lactoferrin as IBD. There is no reliable universal number of days to wait after antibiotics before testing; timing depends on symptoms and the clinical question. Persistent diarrhoea, fever, or abdominal pain after antibiotics needs clinician-led testing rather than self-treatment.

カルプロテクチン vs ラクトフェリン：便検査の選択

トーマス・クライン医学博士

サラ・ミッチェル医学博士

ハンス・ウェーバー教授（博士）