LabreadorLabreador

    Labreador / Bioassay analysis

    ELISA in Excel vs Online

    Excel can fit a 4PL curve using Solver and a carefully checked template. Labreador offers the same model family within a plate workflow, with built-in diagnostics. Neither approach replaces assay validation.

    Open ELISA analysisMethods and references

    Free · No account · Local web calculations · Research use only

    Worked example

    Use the same synthetic 4PL curve as the 4PL calculator: A = 0.1, B = 1.2, C = 16 ng/mL, D = 2.1. A corrected OD of 1.1 gives 16 ng/mL; a dilution factor of 5 gives 80 ng/mL in the original sample. Use identical inputs, blank correction, weighting and constraints when comparing Solver and Labreador.

    1128Concentration (ng/mL), log scale2.10.1Corrected OD
    Synthetic standards, not experimental measurements.

    Equation and units

    Excel layout: A2 = concentration, B2 = corrected mean OD
F2 = A, F3 = B, F4 = C, F5 = D
Predicted OD in C2:
=$F$5+($F$2-$F$5)/(1+(A2/$F$4)^$F$3)
Squared residual in D2:
=(B2-C2)^2
Objective for eight standards:
=SUM(D2:D9)

    Excel Solver workflow

    1. Enable Excel Solver and enter concentrations and blank-corrected standard responses.
    2. Set starting estimates for A, B, C and D; calculate predicted responses and the residual sum of squares.
    3. Minimise the objective with GRG Nonlinear, enforce C > 0, and use a slope sign consistent with the assay direction. Check multiple starting estimates.
    4. Invert the fitted equation only inside the justified calibration range, apply dilution, and inspect recovery and replicates. Or use Labreador's platemap workflow.

    Interpretation and limitations

    Ordinary Excel trendlines do not implement 4PL. Solver can fit the model, and a custom spreadsheet can also implement weighting and QC, but those checks must be designed and maintained. With matched equations and assumptions, converged implementations should agree within numerical tolerance. The zero-dose limit may be mathematically defined for a justified slope convention, but zero cannot be placed on a logarithmic concentration axis. No universal speed or accuracy advantage is claimed.

    Microsoft: define and solve a problem using Solver

    Common questions

    Can Excel calculate a 4PL ELISA standard curve?
    Yes, with Solver and a nonlinear model formula. Built-in chart trendlines are not 4PL regression. You must also implement calibration limits, inverse calculation, dilution and assay quality checks.
    Is an online ELISA calculator more accurate than Excel?
    Not inherently. Compare identical data, model convention, weighting, constraints and convergence. Labreador integrates assay diagnostics and plate handling, while an Excel template can be customised and independently checked.
    Is Labreador a complete Excel or GraphPad Prism replacement?
    No. It is a free task-focused option for supported bioassay and ecotoxicology workflows. Excel and Prism offer broader capabilities; choose according to your experiment and validation needs.

    Related tools and guides

    Open ELISA analysis