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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Rheumatology · Adult-onset Still's Disease

Decoding Your Labs: The AOSD Evidence Trail

At a Glance

There is no single blood test for Adult-onset Still's disease (AOSD). Doctors diagnose it using clinical checklists like the Yamaguchi or Fautrel criteria. Key laboratory indicators include extremely high total ferritin levels combined with a glycosylated ferritin level below 20 percent.

Deciphering your laboratory reports can feel like learning a new language. In Adult-onset Still’s Disease (AOSD), these numbers aren’t just data points; they are the evidence your doctor uses to solve the diagnostic puzzle. Because there is no single “AOSD test,” doctors rely on specific classification criteria—sets of symptoms and lab results that, when combined, point toward a diagnosis [1][2].

The Diagnostic Checklists

To confirm AOSD, your medical team typically uses one of two standardized lists: the Yamaguchi criteria or the Fautrel criteria.

1. The Yamaguchi Criteria

This is the most common checklist. To receive a diagnosis, you generally need at least five criteria, and at least two must be from the “Major” list [1][3].

  • Major Criteria:
    • Fever of 102.2°F (39°C) or higher, lasting at least one week [3].
    • Joint pain or arthritis lasting at least two weeks [3].
    • The classic salmon-colored rash [3].
    • High white blood cell count (leukocytosis) [3].
  • Minor Criteria: Sore throat, swollen lymph nodes, enlarged liver or spleen, and specific liver enzyme elevations [3][4].

2. The Fautrel Criteria

Some doctors prefer this checklist because it includes the “glycosylated ferritin” blood test, which can be more specific for AOSD [5][6]. It has been shown to have a high specificity (about 97.8%) in identifying the disease [6].

Decoding Your Lab Results

Your lab report likely contains several key markers of the “fire” (inflammation) happening in your body.

Ferritin: The Red Flag

Ferritin is a protein that stores iron, but it also acts as an “acute-phase reactant,” meaning its levels skyrocket during intense inflammation [7][8]. In a healthy adult, a normal ferritin level is typically between 15 and 300 ng/mL. In AOSD, ferritin levels are often markedly elevated, frequently exceeding 1,000 ng/mL and sometimes reaching tens of thousands of ng/mL [2][9].

Glycosylated Ferritin: The Huge Clue

Most ferritin in your blood has a sugar molecule attached to it—this is glycosylated ferritin. In healthy people, about 50% to 80% of ferritin is glycosylated. However, in AOSD, this percentage drops significantly, often to below 20% [10][11]. This low percentage is a very strong indicator of AOSD and helps doctors rule out other inflammatory conditions [10][12].

Leukocytosis and the NLR

  • Leukocytosis: This is a high white blood cell count, specifically an increase in neutrophils (your body’s primary “first responder” cells) [13][14].
  • NLR (Neutrophil-to-Lymphocyte Ratio): By dividing your neutrophil count by your lymphocyte count, doctors get a ratio that reflects your body’s stress level. An NLR above 4.0 is a common marker for AOSD activity [11][15].

C-Reactive Protein (CRP)

CRP is a general marker of inflammation in the blood [13]. While it isn’t specific to AOSD, your doctor will monitor it closely to see how well you are responding to treatment. A falling CRP usually means the “fire” is being brought under control [16][17].

Completeness Checklist for Your Lab Reports

When reviewing your records, ensure you have results for:

  • [ ] Total Serum Ferritin (Is it markedly elevated above normal ranges?) [2]
  • [ ] Glycosylated Ferritin % (Is it below 20%?) [10]
  • [ ] Complete Blood Count (CBC) (Check for leukocytosis and calculate your NLR) [13][11]
  • [ ] CRP and ESR (General markers of systemic inflammation) [13]
  • [ ] Liver Function Tests (LFTs) (Check for elevations in AST/ALT) [3]

Common questions in this guide

What are the Yamaguchi criteria for AOSD?
The Yamaguchi criteria is a standardized checklist doctors use to diagnose Adult-onset Still's disease. To receive a diagnosis, a patient usually must meet at least five criteria, including two major signs like a prolonged high fever, joint pain, a salmon-colored rash, or a high white blood cell count.
Why is my ferritin level so high with AOSD?
Ferritin is an iron-storing protein that also acts as an indicator of intense inflammation. In AOSD, ferritin levels often skyrocket well above the normal range, frequently exceeding 1,000 ng/mL, making it a crucial red flag for the disease.
What does a low glycosylated ferritin percentage mean?
Most ferritin in healthy blood has a sugar molecule attached to it, known as glycosylated ferritin. In AOSD, this percentage drops significantly, often falling below 20 percent. This specific drop is a powerful clue that helps doctors distinguish AOSD from other inflammatory diseases.
What does the Neutrophil-to-Lymphocyte Ratio (NLR) mean on my blood test?
The NLR is calculated by dividing your neutrophil count by your lymphocyte count on a complete blood count (CBC) test. It reflects your body's inflammatory stress level. An NLR above 4.0 is frequently used as a marker for active inflammation in Adult-onset Still's disease.
Why does my doctor track my CRP levels?
CRP, or C-Reactive Protein, is a general marker of inflammation in your blood. While it does not specifically diagnose AOSD, doctors closely monitor your CRP levels to see if the inflammation is decreasing and if your current treatment plan is working.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Did I meet the Yamaguchi criteria (requiring 5 total, including 2 major) or the Fautrel criteria for my diagnosis?
  2. 2.What was my exact glycosylated ferritin percentage? Was it below the 20% threshold?
  3. 3.What is my current Neutrophil-to-Lymphocyte Ratio (NLR), and how does it correlate with my disease activity?
  4. 4.Are my ferritin and CRP levels trending downward with my current treatment plan?
  5. 5.Do my lab results show any signs of Macrophage Activation Syndrome (MAS) that we should be watching for?

Questions For You

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References

References (17)
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    A case of adult-onset Still's disease in a patient after a car accident.

    Yaman F, Kimiaei A

    Clinical case reports 2023; (11(8)):e7510 doi:10.1002/ccr3.7510.

    PMID: 37614293
  2. 2

    Recurring Lower Abdominal Pain and Fever as Initial Presentation of Adult Onset Still's Disease in the Absence of Arthralgia and Other System Involvement.

    Sreh A, Rajaiah N, Saim M

    European journal of case reports in internal medicine 2017; (4(6)):000619 doi:10.12890/2017_000619.

    PMID: 30755951
  3. 3

    Expand the differential…think beyond rheumatoid arthritis.

    Schwartz C, Taylor A, Zaidi Z

    BMJ case reports 2018; (2018()) doi:10.1136/bcr-2018-225618.

    PMID: 30249729
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    [Adult-onset Still's disease : Rare adult-onset autoinflammatory syndrome].

    Oms E, Tronnier M

    Der Hautarzt; Zeitschrift fur Dermatologie, Venerologie, und verwandte Gebiete 2019; (70(7)):530-534 doi:10.1007/s00105-019-4394-8.

    PMID: 30937478
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    Adult-Onset Still's Disease-A Complex Disease, a Challenging Treatment.

    Macovei LA, Burlui A, Bratoiu I, et al.

    International journal of molecular sciences 2022; (23(21)) doi:10.3390/ijms232112810.

    PMID: 36361602
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    Validation of the Fautrel classification criteria for adult-onset Still's disease.

    Lebrun D, Mestrallet S, Dehoux M, et al.

    Seminars in arthritis and rheumatism 2018; (47(4)):578-585 doi:10.1016/j.semarthrit.2017.07.005.

    PMID: 28760536
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    Elevated serum gasdermin D N-terminal implicates monocyte and macrophage pyroptosis in adult-onset Still's disease.

    Nagai H, Kirino Y, Nakano H, et al.

    Rheumatology (Oxford, England) 2021; (60(8)):3888-3895 doi:10.1093/rheumatology/keaa814.

    PMID: 33550379
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    Update in Hyperferritinemic Syndromes: Recognition and Management - A Scoping Review.

    Vassilopoulos A, McCormick W, Lakhani A

    The Brown journal of hospital medicine 2022; (1(3)):37667 doi:10.56305/001c.37667.

    PMID: 40046595
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    Predictive factors and prognosis of macrophage activation syndrome associated with adult-onset Still's disease.

    Yang XP, Wang M, Li TF, et al.

    Clinical and experimental rheumatology 2019; (37 Suppl 121(6)):83-88.

    PMID: 31287402
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    Evaluation of Glycosylated Ferritin in Adult-Onset Still's Disease and Differential Diagnoses.

    Guerber A, Garneret E, El Jammal T, et al.

    Journal of clinical medicine 2022; (11(17)) doi:10.3390/jcm11175012.

    PMID: 36078942
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    Proposal of a new diagnostic algorithm for adult-onset Still's disease.

    Daghor-Abbaci K, Ait Hamadouche N, Makhloufi CD, et al.

    Clinical rheumatology 2023; (42(4)):1125-1135 doi:10.1007/s10067-023-06509-8.

    PMID: 36694091
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    Challenges on diagnosis and treatment of refractory adult-onset still disease in Sub-Saharan Africa: a case report.

    Simeni Njonnou SR, Kemta Lekpa F, Essoka Essoka AR, et al.

    Journal of medical case reports 2025; (19(1)):472 doi:10.1186/s13256-025-05477-8.

    PMID: 41029705
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    Adult-Onset Still's Disease: A Case Report.

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    Adult-Onset Still's Disease: Clinical Aspects and Therapeutic Approach.

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    Journal of clinical medicine 2021; (10(4)) doi:10.3390/jcm10040733.

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    Validation of the neutrophil-to-lymphocyte ratio as a new simple biomarker of adult onset Still's disease: A STROBE-Compliant prospective observational study.

    Daghor Abbaci K, Ait Hamadouche N, Otmani F, et al.

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    Elevated White Blood Cell Count and Lactate Dehydrogenase Levels Are Important Markers for Diagnosing Relapse of Adult-onset Still's Disease under Tocilizumab Use.

    Matsushita S, Sada K, Manabe A, et al.

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    Interleukin-6 inhibition: a therapeutic strategy for the management of adult-onset Still's disease.

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    PMID: 34126828

This page explains Adult-onset Still's disease (AOSD) laboratory results and diagnostic criteria for educational purposes only. Always consult your rheumatologist or primary care provider for help interpreting your specific blood tests and medical diagnosis.

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