Get Dust History Testing

Patients and clinicians regularly ask why an ImmunoLytics Dust History (Swiffer) result and an MSqPCR result from the same home can appear to tell different stories. The two are not different versions of one measurement. They use different analytical methods, count different things, and report in different units. This statement sets out what each test answers, how a Dust History percentage should be read, and why a medically sensitive patient requires a stricter criterion than the general population.

What each test measures

Practical consequence: microscopy casts the wider net. If a structure has a cell wall, we can see it, whether or not the organism appears on any published panel. Genera we report routinely, including Curvularia, Bipolaris, Epicoccum, and Myxomycetes, are not among the ERMI 36 and are not among the HERTSMI-2 five. DNA testing, in exchange, delivers species level precision within its panel.

Interpreting a Dust History result

The reported value is the percent of the collected dust surface observed to have mold contamination. It is a graded indicator of mold loading in settled dust, and it should be read against the patient in front of you.

The percentage is only half of the result. Genus identification carries independent weight. Stachybotrys or Chaetomium at any level warrants source investigation regardless of the percentage. Alternaria is strongly antigenic. In our experience, Bipolaris appearing alongside Alternaria, even in trace amounts, is commonly associated with symptomatic occupants. A modest percentage composed of aggressive water damage organisms deserves more attention than a higher percentage composed of ordinary outdoor spores.

Why medically sensitive patients need less than 1 percent

Through AirWell, our indoor air quality inspection company operating in New Mexico since 1980, we separate clients into two groups. The first is a targeted assessment for the general population. The second is an indoor wellness assessment for people with environmentally acquired illness. The clearance criteria for those two groups are deliberately different.

A patient who is already mold sensitized, or who is carrying a measurable toxin burden, is not served by a threshold built around what a healthy occupant tolerates. That patient needs an environment clean enough to permit recovery, and continued low level exposure is enough to prevent it. For this population the criterion is less than 1 percent, and any result above 1 percent should be treated as actionable rather than as the middle of an acceptable range. A result of 5 percent sits visually near the center of the published scale and is easily misread as moderate. For a medically sensitive patient it is a failure.

Post-remediation verification

MSqPCR reports spore equivalents per milligram of dust. That is a concentration, not a quantity, and it does not describe how much mold is in the building.

Consider a home holding a large reservoir of contaminated dust with a HERTSMI-2 score of 30. Remediators then remove 99.99 percent of that dust, an exceptional outcome. If HERTSMI-2 is repeated immediately, the few milligrams of dust that remain can still return a score near 30, because the concentration within the sampled dust has not changed even though the total mold loading of the house has collapsed. The score did not fail to reflect the remediation because the work was poor. It failed because the index is not a measure of building loading.

This is why DNA indices should not be used to clear a remediation job on the day the work is finished, and why competent indoor environmental professionals do not use them that way.

The rule that applies to both platforms: every dust-based method reports a relative measure, so the dust being analyzed must be dust the remediated building actually produced. After remediation, clean thoroughly, allow six to eight weeks for new dust to accumulate, then resample the same locations. A retest run before new dust exists measures the past, not the correction.

Recommended sequence

1. Run the Dust History (Swiffer) microscopy test first, as the broad screen. Collect a composite from the main living areas. It is inexpensive, it is not limited to a fixed species list, and it establishes whether a mold problem exists at all.
2. Use gravity plates room by room to localize the source. Patients frequently find the leak from the plate results alone.
3. Add MSqPCR (ERMI or HERTSMI-2) when a specific Group 1 species question, a CIRS re-entry decision, or a physician protocol requires species level quantitation. Where the patient can afford both, run both: the panels overlap only partially, and a clean result on one platform does not clear the other.
4. Pair dust sampling with air sampling when the question is current airborne exposure rather than accumulated history.
5. Retest six to eight weeks after remediation, sampling the same locations. For a medically sensitive patient, the target is less than 1 percent.

Our position

The two methods are complementary, not competing. Microscopy is the broader screen and the practical first test, because it is not blind to organisms outside a predetermined panel and because it reports the magnitude of mold loading in a form that moves in the right direction when a house is cleaned. DNA panels answer species specific questions with a precision microscopy cannot offer. Neither result clears the other, and discordance between them is usually a difference in what was measured rather than an error by either laboratory.

For clinicians treating medically sensitive patients, the number that matters is straightforward: less than 1 percent on the ImmunoLytics Dust History test.