TSAT and Ganzoni Iron Deficit: Spreadsheet Arithmetic and Units

Two calculations with different inputs

This fictional spreadsheet example demonstrates TSAT and the Ganzoni equation. It does not diagnose iron deficiency or select an intravenous iron prescription. Clinical interpretation and treatment require laboratory context, patient assessment and the relevant product information.

TSAT is the serum iron/TIBC ratio expressed as a percentage. A result alone does not establish the cause of anemia or diagnose hereditary hemochromatosis. Do not turn a single threshold into an automatic diagnosis.

Calculate transferrin saturation

B2 is serum iron and B3 is total iron-binding capacity (TIBC), both in micrograms/dL in this example. The same ratio works if both use matching molar units. Never divide values in different units without converting them first.

E2 returns 12 for 42/350×100, meaning 12 percentage points. Keep this as a general numeric cell or add a percent sign in accompanying text; applying spreadsheet percentage formatting directly to 12 would show 1200%. To use percentage formatting, calculate B2/B3 instead.

The result is not capped at 100. A value above 100 should prompt verification of units, measurements and reporting with the laboratory, not silent replacement with 100.

=IF(COUNT(B2:B3)<>2,"Enter numeric iron and TIBC",IF(OR(B2<0,B3<=0),"Require iron>=0 and TIBC>0",100*B2/B3))

Estimate the iron amount with supplied assumptions

B4 is body weight in kg, B5 the supplied target Hb in g/dL, B6 actual Hb in g/dL and B7 the supplied storage iron allowance in mg. E3 calculates weight×(target−actual)×2.4+stores. With 70 kg, 13−9.5 g/dL and 500 mg stores, the arithmetic gives 1088 mg elemental iron.

The coefficient 2.4 corresponds to Hb in g/dL. For Hb in g/L, the corresponding coefficient is 0.24. Entering 130 and 95 as g/L while retaining 2.4 creates a tenfold error in the Hb-deficit component. The worksheet cannot infer which unit a bare number represents.

Target Hb, weight basis and storage allowance must come from the appropriate method and product guidance. The example target of 13 and stores of 500 are supplied arithmetic assumptions, not a universal adult regimen. Some product information specifies different targets and weight-dependent stores; a weight cutoff must not be treated as universal pediatric authorization.

The estimate is cumulative, not a single infusion amount. This worksheet does not calculate infusion volume, rate, maximum dose per administration, repeat intervals, eligibility or monitoring. These are formulation- and patient-dependent.

=IF(COUNT(B4:B7)<>4,"Complete numeric Ganzoni inputs",IF(OR(B4<=0,B5<=0,B6<=0,B7<0),"Require positive weight and Hb; stores>=0",IF(B5<=B6,"Review target and stores; no automatic dose",B4*(B5-B6)*2.4+B7)))

Do not silently discard the storage component

If target Hb is equal to or below actual Hb, E3 asks for review instead of declaring iron need to be zero. The simple positive-deficit exercise is outside scope in that case; Hb alone does not establish whether iron stores are adequate.

Blank numeric inputs also produce a message. An explicitly supplied zero storage allowance is accepted as an arithmetic assumption. This is different from leaving the cell blank and accidentally treating it as zero.

Explore independent changes

Double both serum iron and TIBC: TSAT remains 12. Double weight to 140 kg with the other fictional inputs unchanged: the Hb component doubles from 588 to 1176 mg, while the supplied storage term stays 500, making 1676 mg.

Change B7 from 500 to 300: the estimate falls by exactly 200 mg to 888 mg. This demonstrates the equation, not a reason to change an actual prescribed storage allowance.

Further reading

• Venofer — Summary of Product Characteristics, section 4.2
• Medsafe — Ferrosig data sheet, Ganzoni equation in g/L
• National Kidney Foundation KDOQI — Evaluation of Anemia in CKD