What is the Sokal score?

The Sokal prognostic index is a formula published in 1984 by Sokal et al. that uses age, spleen size, platelet count, and blast percentage to predict survival in chronic myelogenous leukemia. It remains widely used alongside the EUTOS and Euro scores.

What are the risk cut-offs?

Low risk: score 1.2. Higher scores correlate with shorter survival and lower rates of complete cytogenetic response.

How is spleen size measured?

Spleen size in the Sokal formula is the palpable distance in centimeters below the left costal margin. Enter 0 if the spleen is not palpable on physical examination.

Does the Sokal score apply to patients on TKIs?

The Sokal score was derived from chemotherapy-era data (busulfan/hydroxyurea). It still predicts response to imatinib and second-generation TKIs, but the EUTOS long-term survival (ELTS) score is preferred for the TKI era per some guidelines.

What platelet unit does the formula use?

The formula uses platelets in units of 10⁹/L (same as 10³/µL or thousands/µL). A typical normal value is 150–400 × 10⁹/L.

Sokal CML Prognostic Score

Enter age, spleen size, platelet count, and blast percentage to get the Sokal score and CML risk group.

Patient Parameters

Age (years)

Spleen size (cm below costal margin; 0 if not palpable)

Platelet count (× 10⁹/L)

Peripheral blood blasts (%)

Enter patient values and click Calculate to see the Sokal score.

Sokal Formula

Score = exp(
  0.0116 × (age − 43.4)
  + 0.0345 × (spleen − 7.51)
  + 0.188 × ((platelets/700)² − 0.563)
  + 0.0887 × (blasts − 2.10)
)

Low risk: Score < 0.8

Intermediate risk: Score 0.8 – 1.2

High risk: Score > 1.2

Done

Summary

The Sokal score is the most widely used prognostic index for chronic myelogenous leukemia (CML). It combines age, spleen size, platelet count, and peripheral blast percentage into a single exponential formula that classifies patients into low (< 0.8), intermediate (0.8–1.2), or high (> 1.2) risk groups. This tool computes the score instantly in your browser with no data sent to any server.

How it works

Enter patient age in years.
Enter spleen size in centimeters below the costal margin (0 if not palpable).
Enter platelet count in units of 10⁹/L.
Enter peripheral blood blast percentage.
The Sokal score is computed using the validated exponential formula.
Risk group (Low / Intermediate / High) is displayed with the numeric score.

Use cases

Stratify newly diagnosed CML patients before starting therapy.
Compare risk profile across clinical trial cohorts.
Estimate prognosis for CML patients in the chronic phase.
Support treatment decisions when selecting TKI intensity.
Teach medical students the Sokal scoring formula.

Frequently Asked Questions

Last updated: 2026-06-15 · Reviewed by Nham Vu