Every New Code Is a New Count

On October 1 I celebrated—maybe with some of you?—FY2027 going live, but medetomidine was what I couldn't stop thinking about. One drug finally picked up one new subcategory, T65.85-, making its toxic effects countable.

I’m talking in an epidemiologist's sense. Prevalence and incidence both start with a tally of cases. In claims and administrative data, a case gets included when it gets assigned an ICD-10-CM diagnosis.

Uncoded means unseen

Those datasets are built from billed and abstracted encounters. A condition without its own code may well be written in a progress note. By the time the visit finds its way into a claims file, it has been folded into a broader category, where it can't be told apart from its neighbors.

Researchers work around those gaps. A 2024 paper on blast exposure mentions that proxy measures such as military occupational specialty are frequently used, especially for retrospective chart review studies. Well, a job title is an educated guess about who was probably in harm's way, but a dedicated code lets the record speak for itself.

FY2027 adds a bunch of these to category Z77, Other contact with and (suspected) exposures hazardous to health. Here’s each code, checked against the NCHS release files and the CMS 2027 files.

Z77.32: burn pits

Z77.32, Contact with and (suspected) exposure to burn pits in war theater.

Under VA rules, anyone who served in Iraq, Kuwait, and several other countries on or after August 2, 1990, or in Afghanistan and others on or after September 11, 2001 is assumed to have had toxic exposure. The PACT Act of 2022 added more than 20 presumptive conditions tied to those hazards, including COPD and asthma diagnosed after service.

The request came through the Federal Electronic Health Record Modernization (FEHRM) office, saying ICD-10-CM had no code that could adequately cover open burn pit exposure, and it listed a "potentially inaccurate understanding of the prevalence of burn pit exposure among military personnel" among the consequences. That is about as epidemiological as they get.

Z77.33: Agent Orange

Z77.33, Contact with and (suspected) exposure to Agent Orange.

VA presumes exposure for service in the Republic of Vietnam between January 9, 1962, and May 7, 1975, plus a few other places. The PACT Act put hypertension and monoclonal gammopathy of undetermined significance (MGUS) on the list of conditions VA links to the herbicide, and it added five locations, among them Thailand and Laos.

Interestingly, there's a short coding history here, too. FY2026 created Z77.39, Contact with and (suspected) exposure to other war theater, and listed "Agent Orange exposure" as an inclusion term under it. The FY2027 tabular addenda strike it, and the index entry moves from Z77.39 to Z77.33. For one fiscal year, then, these cases were mixed into a catch-all. Anyone trying to build a trend line across October 2026 needs to figure out how to handle that break.

Z77.40–Z77.42 and Z77.49: blast overpressure

Z77.40, Contact with and (suspected) exposure to unspecified blast overpressure

Z77.41, Contact with and (suspected) exposure to low-level blast overpressure

Z77.42, Contact with and (suspected) exposure to high-level blast overpressure

Z77.49, Contact with and (suspected) exposure to other blast overpressure

The Defense Health Agency's Traumatic Brain Injury Center of Excellence asked for these. Its proposal says they are meant to capture low-level and high-level exposures that fall short of DoD's TBI criteria, and it cites an August 8, 2024, memo from the Deputy Secretary of Defense on managing brain health risks from blast overpressure. FY2026 had already added external cause codes for these events in war (Y36.A-) and military operations (Y37.A-).

Rowland and Martindale point out that blast exposure does not typically result in TBI. Brain injury has several accepted definitions, they note, and the exposure itself has none. When they reanalyzed one cohort of combat veterans with five competing yardsticks, the associations with symptoms and cognitive testing shifted with the choice. A national code with a low-level/high-level split gives claims data a shared label to start from. Their bigger question, which blasts should qualify in the first place, stays open.

Z77.013: gadolinium

Z77.013, Contact with and (suspected) exposure to gadolinium.

This one goes in Z77.01, hazardous metals, the same subcategory as lead (Z77.011). Gadolinium is the element in the contrast agents sometimes injected for MRI scans. In 2017 FDA required a class warning because the metal can remain in the body, including the brain, for months to years. The agency also said retention had not been directly linked to adverse health effects in people with normal kidney function. To date, the one known harm tied to it was nephrogenic systemic fibrosis, a rare disorder seen in a small subgroup with pre-existing renal failure. Regulators flagged those needing multiple lifetime doses, pregnant women, children, and patients with inflammatory conditions as possibly higher-risk.

The request arrived inside a proposal titled "Gadolinium Induced Gout," and the arthritis codes it sought aren't in the FY2027 files. A related lab-finding code did make it in: R78.72, Abnormal gadolinium level in blood, with an Excludes1 note for toxic effect of gadolinium (T56.82-).

Who asks

Medetomidine's first-year count depends on lab testing. For new Z77 entries, the bottleneck is the interview. Each code records a history, which gets written down when a clinician asks or a patient brings it up.

The official guidelines say Z77 indicates contact with and suspected exposures hazardous to health, and that contact/exposure codes appear first-listed to explain a testing encounter or, more commonly, in a secondary position to flag a potential risk. Assignment rests on what the provider documents. If the chart doesn't mention deployment or contrast, a coder has no basis to report either one.

That makes the setting matter. The PACT Act requires VA to provide a toxic exposure screening to enrolled Veterans, with a follow-up at least once every five years, and the screening asks about open burn pits and Agent Orange by name. Someone seen at a walk-in clinic for a cough falls outside that VA workflow. For gadolinium, FDA's advice to patients is to tell their health care professional the date of their last MRI with gadolinium, which makes some of the recordkeeping fall on the patient's memory. I'd expect uneven capture, heaviest where an intake form prompts for the history.

Now, one more bit of caution. A Z77 code records contact with something that might be harmful, and the category's own includes note calls these potential hazards to health. Illness and injury get their own codes elsewhere in the classification. The tabular draws a clear line for gadolinium, where the abnormal lab finding excludes the toxic effect subcategory (T56.82-). A tally of Z77.32 tells you how many encounters documented burn pit exposure. Whether any of those people were harmed needs totally different data to answer.

What a year or two of data might show

By late 2027 or 2028, I think an epidemiologist could reasonably measure a handful of things.

Uptake. Monthly counts of each new Z77 code by setting would trace how documentation habits spread. In the first year that curve will mostly reflect who started asking. It's still useful, as long as it isn't read as an exposure trend.

Specificity. Within the blast subcategory, the share of encounters coded Z77.40 (unspecified) versus Z77.41 and Z77.42 is a ready-made data quality indicator. If Z77.40's slice shrinks over time, clinicians are probably documenting the low-level/high-level distinction the requesters wanted.

The Agent Orange handoff. Z77.39 volume should drop in FY2027 while Z77.33 picks up. Checking FY2026 Z77.39 totals against FY2027 Z77.33 plus Z77.39 is a decent sanity test on whether the reclassification behaved as expected.

Co-occurrence. Among encounters carrying Z77.32, an analyst could describe how often respiratory diagnoses on the VA presumptive list also appear, compared with a reference group. Who gets asked about exposure is far from random, so these numbers would reflect documentation patterns as much as risk. Treat them as hypothesis material.

Gadolinium history and blood levels. Z77.013 and R78.72 can each be tallied in the same datasets. The tabular has no instructional note tying the two together, so any overlap an analyst finds comes from charting habits, and neither line establishes harm.

Each of these is a numerator. Turning one into a rate needs a denominator, like the total of patients who had a contrast MRI. The problem is, claims data usually can't supply that by itself.