Calculator Guides
DAS28: Check the Inputs Before Interpreting the Trend
Editorial record
This source-linked educational article has been updated through AI-assisted evidence checks and editorial review. Verify information against current guidance and local protocols before applying it to patient care.
Citation methodologyA fall in DAS28 is useful only when the assessments are comparable. Changing the laboratory marker, the patient-global scale, or the joints examined can create an apparent improvement without a matching clinical change.
Four Inputs, Two Different Equations
The four-variable DAS28-ESR uses tender and swollen counts from 28 joints, ESR in mm/hour, and patient global health on a 0-100 scale:
0.56 * sqrt(TJC28) + 0.28 * sqrt(SJC28) + 0.70 * ln(ESR) + 0.014 * GH
Use the natural logarithm. ESR must be positive; missing values are not zero. Developer's calculation instructions.
DAS28-CRP is a separate validated equation, not the ESR formula with a different lab result inserted:
0.56 * sqrt(TJC28) + 0.28 * sqrt(SJC28) + 0.36 * ln(CRP + 1) + 0.014 * GH + 0.96
Use CRP in mg/L. If the global assessment is absent, use an explicitly validated three-variable version rather than assigning zero. Alternative equations.
A Tenfold Input Error
For a fictional visit with TJC28 = 4, SJC28 = 2, ESR = 20, and GH = 40:
1.12 + 0.39598 + 2.09701 + 0.56 = 4.17299, or 4.17.
Entering GH = 4 instead of 40 gives 3.67. That half-point difference is an input error, not treatment response. If the same visit has CRP = 10 mg/L, its DAS28-CRP is 3.90. Record the version beside every total.
Count the Full Joint Set
The 28-joint set includes both shoulders, elbows, wrists, knees, ten MCP joints, and ten hand interphalangeal joints, including the thumb IP joints. Omitting the thumbs leaves only 26. Feet and ankles are outside this count, so examine symptomatic areas even when the composite is low. Original 28-joint index.
A Category Is Not a Prescription
Conventional DAS28-ESR bands are remission below 2.6, low activity from 2.6 through 3.2, moderate activity above 3.2 through 5.1, and high activity above 5.1. Avoid overlapping categories at 3.2. These labels do not establish that every painful joint is inflamed or that clinical remission is complete. DAS28-CRP is not numerically interchangeable with DAS28-ESR; use the version and interpretation specified by the clinical protocol rather than assuming identical classification. DAS28 developer resource.
Discuss the joint examination, trend, function, comorbidities, and prior treatment with the rheumatology team. A single high result does not create universal biologic eligibility, and a single low result does not justify tapering. The EULAR 2025 update, published in 2026, uses a treat-to-target strategy. After glucocorticoids have been stopped and remission is sustained, it recommends continuing DMARDs while allowing consideration of dose reduction; routine withdrawal is not the default. Current EULAR recommendations.