Source: https://guthlabs.ai/docs/instruments/lung-capacity-predicted-values-spirometry-reference/mechanism/

instrument mechanism / verified-clean

# Lung Capacity Predicted Values (Spirometry Reference) mechanism

The inspectable method record for Lung Capacity Predicted Values (Spirometry Reference), kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The arithmetic fixtures verify only ratio and percentage post-processing using explicitly supplied provisional reference values. They do not verify the GLI-2012 demographic prediction itself. Before PASS, supply the authoritative GLI-2012 coefficient/table dataset, source/version, ethnic-group mapping, LMS equation including z=0 convention, valid ranges, interpolation rules, missing-data behavior, rounding policy, and an explicit decision on whether %predicted for FEV1/FVC is offered.

- The specification names GLI-2012 but does not provide the required GLI-2012 LMS coefficients, spline knots, coefficient version, or calculation algorithm, so the claimed predictions cannot be independently reproduced from this specification.

- GLI-2012 is ordinarily implemented with sex-, age-, height-, and ethnic-group-specific L, M, and S parameters and z-score equations; a generic lookup-table description is insufficient unless the exact table and interpolation rules are supplied.

- The permitted ethnicity categories and mapping are unspecified. GLI-2012 uses defined reference groups, and an arbitrary ethnicity label or race/ethnicity mapping can produce materially different results.

- The specification does not state whether age is decimal years or completed years, whether height is standing height in centimetres, or which sex definition and valid age range are used.

- It is ambiguous whether predicted FEV1/FVC means the quotient of predicted FEV1 divided by predicted FVC or a separately predicted GLI-2012 ratio/z-score quantity.

- %predicted is not generally a clinically appropriate summary for FEV1/FVC; the ratio is commonly interpreted with its own reference distribution or z-score, not simply as a percentage of predicted ratio.

## Units and conventions

- Age is assumed to be in years and within the validated GLI-2012 range of approximately 3 through 95 years.

- Height is assumed to be standing height in centimetres; no automatic conversion from inches is assumed.

- FVC and FEV1 are assumed to be in litres (BTPS-adjusted spirometric values).

- Ratios are dimensionless and are reported here as a decimal rather than a percentage.

- The provisional table rows below are explicit test fixtures for arithmetic and post-processing only; they are not a substitute for the missing official GLI-2012 coefficient tables.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "age_years": 25,
    "height_cm": 180,
    "sex": "male",
    "ethnicity": "Caucasian",
    "measured_FVC_L": 5,
    "measured_FEV1_L": 4
  },
  "expected_outputs": {
    "predicted_FVC_L": 5.5,
    "predicted_FEV1_L": 4.4,
    "predicted_FEV1_FVC_ratio": 0.8,
    "FVC_percent_predicted": 90.91,
    "FEV1_percent_predicted": 90.91
  },
  "reference_data": {
    "predicted_FVC_L": 5.5,
    "predicted_FEV1_L": 4.4,
    "source_convention": "GLI-2012 spirometry reference convention; provisional arithmetic test fixture, not an official coefficient-table extract"
  },
  "working": "Predicted ratio = predicted FEV1 / predicted FVC = 4.4 / 5.5 = 0.800000. FVC %predicted = 5.0 / 5.5 x 100 = 0.9090909 x 100 = 90.91%. FEV1 %predicted = 4.0 / 4.4 x 100 = 0.9090909 x 100 = 90.91%."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The specification cannot produce numerical predicted FVC, FEV1, or ratio outputs because the required GLI-2012 coefficient tables and exact validity/switch definitions are missing. In addition, measured FEV1/FVC with measured FVC = 0 creates an undefined 0/0 result that must be explicitly rejected or reported as undefined.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/lung-capacity-predicted-values-spirometry-reference/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/lung-capacity-predicted-values-spirometry-reference/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/lung-capacity-predicted-values-spirometry-reference/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`