Type 1 Diabetes Staging Classifier

Assign the correct stage of type 1 diabetes to a person with detectable islet autoantibodies. Staging determines monitoring intensity, eligibility for disease-modifying therapy (teplizumab), and whether insulin is required.

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Step 1 — Confirm the autoantibody status is real

Before staging, verify:

• The positive screen has been confirmed in a second sample — a single positive result is not sufficient
• Confirmation used two independent laboratory methods (e.g. radiobinding assay + ELISA)
• The specific antibodies are documented (GAD65 / IAA / IA2 / ZnT8)
• Negative status for the OTHER islet autoantibodies has been confirmed on the same second sample

If any of the above is missing → arrange confirmation testing before staging. An unconfirmed positive cannot be staged.

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Step 2 — Count the confirmed autoantibodies

Confirmed autoantibody count	Direction
0 (all negative on confirmation)	Not T1D by antibody criteria. Consider other causes of hyperglycaemia if present
1 confirmed (single positive, second sample positive for the SAME antibody with 2 methods)	At Risk (see Step 4)
Transient single positive (second sample negative)	At Risk — arrange repeat testing per Step 4
≥2 confirmed	Proceed to Step 3 to assign Stage 1, 2, or 3

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Step 3 — Combine antibody count with glycaemic status

Get the person's most recent glycaemic profile:

• Fasting plasma glucose (FPG) in mmol/L (mg/dL)
• 2-hour value on OGTT
• HbA1c in mmol/mol (%)
• If available, CGM data — % time above 7.8 mmol/L (140 mg/dL)
• Presence or absence of osmotic symptoms (polyuria, polydipsia, weight loss)

Apply this table (in order — assign the FIRST matching row):

Autoantibodies	Glycaemia	Symptoms	Stage
≥2 confirmed	Normal (FPG <5.6 mmol/L / <100 mg/dL, 2h OGTT <7.8 mmol/L / <140 mg/dL, HbA1c <39 mmol/mol / <5.7%)	Asymptomatic	Stage 1
≥2 confirmed	Mild dysglycaemia: ≥1 of — FPG 5.6–6.9 mmol/L (100–124 mg/dL) / 2h OGTT 7.8–11.0 mmol/L (140–198 mg/dL) / HbA1c 39–47 mmol/mol (5.7–6.4%)	Asymptomatic	Stage 2a
≥2 confirmed	Notable dysglycaemia below ADA thresholds: one of the Stage 2a glycaemic indicators AND CGM time >7.8 mmol/L (>140 mg/dL) of >10%	Asymptomatic	Stage 2b
≥2 confirmed	Meets ADA diagnostic criteria for diabetes (FPG ≥7.0 mmol/L / ≥126 mg/dL on two occasions, OR 2h OGTT ≥11.1 mmol/L / ≥200 mg/dL, OR HbA1c ≥48 mmol/mol / ≥6.5%, OR random glucose ≥11.1 mmol/L with symptoms)	Asymptomatic	Stage 3a
≥2 confirmed	Meets ADA diagnostic criteria	Symptomatic (osmotic symptoms, weight loss, DKA)	Stage 3b
Present	Established insulin-treated T1D of long duration	—	Stage 4

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Step 4 — Special case: single or transient single autoantibody ("At Risk")

Confirmed single autoantibody positive (second sample confirms the same antibody, other antibodies negative):

• ~10–15% risk of progression to Stage 3 T1D over 15 years (vs 0.3% general population)
• Retesting and glucose monitoring is less stringent than for multi-antibody individuals
• No indication for teplizumab at this stage
• Retest islet autoantibodies periodically (e.g. annually or per local protocol) — a person can progress from single to multiple antibodies
• Education about T1D symptoms (osmotic symptoms, weight loss, DKA) is still valuable

Transient single positive (initial positive, second sample negative):

• Interpret as "at risk" — the antibody may fluctuate
• Repeat testing within an appropriate interval (e.g. 6–12 months)
• Do NOT stage as Stage 1 unless ≥2 antibodies are confirmed

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Step 5 — Downstream action per stage

Once stage is assigned, the management pathway is:

Stage	Priority action
At Risk	Retesting cadence, symptom education, no monitoring program
Stage 1	Enrol in early-stage T1D monitoring program (education, glucose monitoring, psychological support, DKA prevention). No disease-modifying therapy yet
Stage 2 (2a or 2b)	Enrol in monitoring program AND evaluate teplizumab eligibility — Stage 2 is the approved indication in FDA, EMA, MHRA, Health Canada
Stage 3a (asymptomatic)	May not need insulin immediately; some evidence supports observation with close monitoring, others start insulin. Individual decision
Stage 3b (symptomatic)	Insulin therapy required — standard T1D management. Assess for DKA at presentation
Stage 4	Standard long-term T1D management (glucose monitoring, complication surveillance, comorbidity management)

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Guardrails

• Never stage on a single positive screen without confirmation — single unconfirmed positives are common false positives. Staging on unconfirmed data leads to overdiagnosis, unnecessary anxiety, and potentially inappropriate therapy
• Stage 3 is a biochemical diagnosis, not a symptom diagnosis — a person can meet ADA criteria without osmotic symptoms (Stage 3a). Do not withhold the T1D label just because they feel well
• A person can move between stages — retest glycaemia at each contact. A Stage 1 individual may become Stage 2 with mild FPG rise; a Stage 2 can progress to Stage 3 over weeks to months in adolescents
• Osmotic symptoms at any point trigger urgent evaluation — do not wait for a scheduled visit. Educate the family/patient to seek care immediately for polyuria/polydipsia/weight loss/vomiting
• DKA at presentation is a preventable failure — the whole point of staging early is to catch progression BEFORE DKA. If a monitored person presents in DKA, review why the monitoring didn't detect the transition earlier
• Stage 3a is genuinely controversial — some clinicians and guidelines start insulin at Stage 3a (biochemical); others observe carefully with rapid escalation ready. Discuss both approaches with the patient/family and document the shared decision
• Progression to Stage 3 approaches 100% in children/adolescents with confirmed ≥2 autoantibodies — this is not "risk" language; it is near-certainty. Communicate it appropriately without inducing distress. Progression is slower in adults (research ongoing)
• Progression risk is not the same as immediate diabetes — average time from Stage 1 to Stage 3 in children is years, and in adults is likely longer. There is time to prepare
• Stage 2b (CGM-defined) requires CGM data — if CGM is not available, use whichever Stage 2a criterion is met and label as Stage 2 (subtype not further specified)
• HbA1c can miss early dysglycaemia — in a person with ≥2 autoantibodies and normal HbA1c, still perform OGTT or arrange CGM before concluding "Stage 1"

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Related MD2SKILL skills

• t1d-islet-autoantibody-screening-confirmation — how to run the screen and confirm a positive
• teplizumab-eligibility-and-course — for Stage 2 T1D
• nd-t2d-oad-selector — if the diagnosis turns out to be T2DM, not T1DM (distinguishable partly by autoantibody status)
• gcih-patient-classifier — for inpatient hyperglycaemia distinguishable from new-onset T1D

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Source

Hussain S, Tree T, Mathieu C, Klupa T, Tuomaala A-K, de Wit M, Kordonouri O, Braune K, Pall J, Castano L, Besser REJ, Galhardo J, Ulivi F, Bosi E, Bogdanovic U, Alabert C, Battelino T. An international consensus on screening and monitoring early-stage type 1 diabetes: A roadmap to European implementation. Diabetes, Obesity and Metabolism. 2026;28:3535–3556. DOI: 10.1111/dom.70569. Open-access under Creative Commons Attribution (CC-BY). Section 3 and Figure 1.