Which Interpretation Method and Predicted Values to Use for Spirometry

What's happening

The CCS-200 ships with several selectable interpretation methods and predicted/reference value sets, and it's a common question which one to actually use for occupational testing. The choice isn't just a preference setting — the wrong reference set changes whether a given subject's results grade as normal or abnormal.

Interpretation methods available on the CCS-200 are ATS 1991, NLHEP, and Morris 1976 (NLHEP and Morris 1976 require the Plus Package). Separately from the interpretation method, the software also lets you select which predicted/reference value set to compare a subject's results against. Without the Plus Package, the choices are NHANES III and Knudson 1976; with the Plus Package, GLI-2012, Knudson 1983, Crapo, and Morris are also available. NHANES III (also referred to by the manual as Hankinson 1999) is the set most commonly used for occupational surveillance testing, in part because it's the only set that provides separate reference equations for African American subjects rather than applying a flat race-correction factor. If you're setting up occupational testing and aren't working from a specific program requirement that calls for a different reference set, NHANES III (Hankinson 1999) is the one to confirm is selected.

We can't confirm a blanket OSHA mandate for NHANES III from the Benson manuals — if your testing program is governed by a specific OSHA, MSHA, or state regulation, check that regulation's own language rather than relying on this guide for the citation.

Where the setting lives

1. The interpretation method and reference value set are set in the Company dialog, reached from the Control Window's File menu > Company. If you're on the Plus Package, you can also reach this through Modify Company.
2. Confirm the reference set currently selected before assuming it's already correct — this is a per-company setting, and it's worth checking rather than guessing, especially on an install that's been in place a long time or was set up by someone who's since left.
3. The CCS-200 user manual's Companies and Subjects chapter covers the Interpretation and Predicted Normals settings themselves; the Test Records chapter's Spirogram Analysis section covers the full list of predicted value sets and which indices each one supports, if you want the underlying detail.

Before you change it — read this

Changing the interpretation method or reference value set triggers a full reanalysis of every spirogram already stored for that company. This is not a quick, reversible toggle: once the reanalysis starts, it cannot be aborted partway through. Every existing test in that company gets reinterpreted against the new reference set, which changes how those historical results are graded and displayed going forward.

Confirm you actually want this before you click through the prompt. If you're not sure whether changing the setting is the right move for a company with a long testing history, it's worth a call to us first rather than starting a reanalysis you can't stop partway through.

When to call us

• You're not sure which reference set is currently selected, or whether it's ever been changed.
• You need to change the setting on a company with a substantial history of stored spirograms and want to talk through what the reanalysis will change before you start it.
• You're setting up occupational testing for the first time and want confirmation that NHANES III (Hankinson 1999) is correctly selected before testing begins.

You can reach us at (513) 891-0868 or service@fosterinstruments.com.