An 8-year-old girl presents to the clinic with a 2-year history of inattention, poor academic performance, and difficulty following instructions at home and school. Her parents report that she is often forgetful and loses things frequently. Before confirming ADHD, which investigation is most appropriate to exclude a common secondary cause?

## Screening for Secondary Causes Before ADHD Diagnosis **Key Point:** Before diagnosing ADHD, it is essential to rule out secondary causes that present with inattention and poor academic performance. Hearing loss is a common, treatable cause that mimics ADHD symptoms, particularly inattention and apparent non-compliance. ### Why Audiometry is the Most Appropriate Investigation **High-Yield:** Undetected hearing loss in children can present as: - Inattention and difficulty following instructions (child cannot hear) - Poor academic performance (cannot process auditory information) - Behavioral problems (frustration from communication difficulty) - Social withdrawal and apparent "forgetfulness" **Clinical Pearl:** A child with hearing loss may be misdiagnosed as having ADHD because the symptoms overlap significantly. Audiometry is a simple, non-invasive, inexpensive screening tool that should be performed in all children with suspected ADHD before confirming the diagnosis. ### Secondary Causes to Screen Before ADHD Diagnosis | Condition | Presentation | Screening Investigation | |---|---|---| | **Hearing loss** | Inattention, poor comprehension, behavioral issues | Audiometry, age-appropriate hearing assessment | | **Thyroid disorder** | Inattention, poor concentration, fatigue | TSH, free T4 | | **Sleep apnea/sleep disorder** | Inattention, hyperactivity, poor school performance | Sleep history, polysomnography if indicated | | **Lead toxicity** | Inattention, hyperactivity, behavioral problems | Serum lead levels | | **Anemia** | Inattention, fatigue, poor concentration | Hemoglobin, hematocrit | | **Vision problems** | Inattention during visual tasks, poor academic performance | Visual acuity testing, refraction | **Mnemonic:** **HATS-LAV** — **H**earing loss, **A**nemia, **T**hyroid disorder, **S**leep disorder, **L**ead toxicity, **A**cid-base/metabolic issues, **V**ision problems — common secondary causes to exclude before ADHD diagnosis. ### Diagnostic Approach ```mermaid flowchart TD A[Child with suspected ADHD symptoms]:::outcome --> B[Detailed history & clinical examination]:::action B --> C[Screen for secondary causes]:::action C --> D{Hearing assessment}:::decision D -->|Abnormal| E[Refer to ENT/Audiology]:::action D -->|Normal| F[Screen thyroid, lead, sleep history]:::action F --> G{All screens normal?}:::decision G -->|Yes| H[Proceed to CPT/neuropsych testing]:::action G -->|No| I[Investigate & treat identified condition]:::action H --> J[Confirm ADHD if criteria met]:::outcome ``` **Tip:** Always obtain a detailed developmental and medical history, including perinatal complications, infections, and medication exposure. Vision and hearing screening should be part of the baseline assessment in all children with learning or behavioral difficulties. [cite:American Academy of Pediatrics ADHD Diagnostic Guidelines; DSM-5]