Somewhere in your child's after-visit summary, there's a line of lab orders that reads like a different language. "CMA, peripheral blood." "Exome sequencing, trio." Maybe just "chromosome analysis." Those few words determine whether your child's genetic evaluation follows current medical guidance or an approach the field moved past years ago.

The American Academy of Pediatrics updated its guidance on genetic testing for children with global developmental delay and intellectual disability, naming chromosomal microarray and exome sequencing as first-tier tests. First-tier means these are the tests to start with, not the tests you graduate to after everything else comes back normal. For parents, the update turns those cryptic lab orders into something you can check: does what the doctor ordered match what the evidence says works?

I find this shift genuinely exciting, because it reflects how far the testing itself has come. A decade ago, starting with the most powerful test meant an enormous bill and months of waiting. Today the yields are higher, the costs have dropped, and the AAP guidance has caught up with the science.

What First-Tier Testing Means Under the AAP Guidelines

Roughly 40% of children with global developmental delay or intellectual disability have an identifiable genetic cause. The question has never been whether to look, but where to look first.

For years, the standard sequence started small: a karyotype to check chromosome structure, maybe fragile X testing, then chromosomal microarray if those came back normal, then sequencing as a last resort. Each round meant another blood draw, another insurance authorization, another stretch of waiting.

The updated AAP guidance compresses that ladder. Chromosomal microarray and exome sequencing sit at the front of the line, because they answer the question far more often. Microarray identifies a cause in roughly 15-20% of children with unexplained delays. Exome sequencing finds a diagnosis in 36-53% of cases. A karyotype alone, the old default, catches only large chromosome rearrangements and misses most of what those two tests detect.

Fragile X testing still has a place when the clinical picture or family history points to it. What no longer fits current guidance is a workup that stops at karyotype and calls the evaluation complete.

How to Read the Test Names on the Order

Each test reads DNA at a different zoom level, and once you see that, the jargon starts to make sense.

Chromosomal microarray (CMA) scans for missing or duplicated chunks of DNA, the kind of change involved in conditions like DiGeorge syndrome or Angelman syndrome. It reads in chunks, not letters. Research on autism shows microarray identifies a cause in about 10% of cases, which is exactly the kind of change this zoom level is built to catch.

Exome sequencing (WES) reads the protein-coding portion of the genome letter by letter. That's about 2% of your child's total DNA, but it's the 2% where most known disease-causing variants live. This is the test that catches the small spelling changes a microarray can't see.

Genome sequencing (WGS) reads everything, including the regulatory regions between genes. It's the widest lens available, and some centers now offer it in place of exome sequencing. The tradeoffs between the two are real, and we've compared them in detail in our guide to chromosomal microarray versus whole genome sequencing.

Karyotype is the oldest of the four, a photograph of the chromosomes under a microscope. It still matters for specific situations, like suspected Down syndrome or certain rearrangements, but it was never designed to find the small variants behind most unexplained delays.

If the order lists "trio," the lab wants DNA from your child and both biological parents. Comparing all three genomes helps the lab separate variants your child inherited from ones that appeared new, which sharpens the interpretation considerably.

If Your Child Was Tested Years Ago

Genetics moves fast enough that the year on the lab report matters. A child evaluated in 2015 with a normal karyotype and normal fragile X had a guideline-appropriate workup for 2015. By today's standard, that evaluation never looked where most answers are found.

Re-evaluation is a reasonable request, not a complaint about past care. Ask the pediatrician or geneticist two things: which genetic tests has my child had, and would current AAP guidance recommend anything we haven't done? Even families whose child had a microarray may be candidates for exome sequencing now, since the tests look at different kinds of changes.

Labs also reanalyze old sequencing data as new gene-condition links are published, a detail that delights me every time I get to share it with a family. If your child had exome sequencing more than two or three years ago with no diagnosis, asking the ordering provider about reanalysis can surface an answer without a single new blood draw.

Questions That Get the Right Tests Ordered

You don't need to memorize diagnostic yields to advocate well at the appointment. A few direct questions do the work:

• Which specific genetic tests are you ordering, and are they first-tier under current AAP guidance?
• If we're starting with microarray, what's the plan if it comes back normal?
• Should we do trio testing, and does the lab need samples from both parents?
• Will a genetic counselor walk us through the results, whatever they show?

Insurers sometimes approve the older, cheaper tests and balk at sequencing. The AAP's first-tier designation is your strongest tool in that fight, because it establishes the test as standard of care rather than an extra. If you hit a denial, the appeal process is winnable more often than families expect, and we've laid out the steps in our guide to fighting an insurance denial for your child's evaluation.

Results bring their own set of questions, from clear diagnoses to variants of uncertain significance, and our overview of what the AAP guidelines mean for your family walks through that side of the process.

Before the next appointment, pull out the old lab reports and the new orders, and read the test names with your new zoom-level lens. If the workup starts and ends with a karyotype, you now know the question to ask, and you know the AAP is standing behind you when you ask it.