Is it necessary to proceed with the ordered laboratory tests for a 21-year-old female patient with chronic exertional compartment syndrome, symptoms concerning for restless legs syndrome, iron deficiency, and a mildly elevated lipid profile?

Laboratory Testing for 21-Year-Old Female with CECS, RLS Symptoms, Iron Deficiency, and Dyslipidemia

Yes, proceed with comprehensive laboratory testing—this patient requires iron studies (ferritin and transferrin saturation), complete blood count, lipid panel, renal function, and thyroid function to properly diagnose and manage her suspected restless legs syndrome and assess cardiovascular risk. 1, 2

Essential Iron Studies for RLS Diagnosis

Check morning fasting serum ferritin and transferrin saturation immediately, as these are mandatory for any patient with suspected RLS. 1, 2 The American Academy of Sleep Medicine requires both parameters because:

• Ferritin alone can be falsely elevated by inflammation, making transferrin saturation essential to identify functional iron deficiency even when ferritin appears adequate 1
• RLS-specific iron thresholds differ from general population: supplement if ferritin ≤75 ng/mL OR transferrin saturation <20% 1, 2
• Women have 5.51 times higher risk of iron deficiency without anemia (IDNA) in RLS, making screening particularly critical in your 21-year-old female patient 3
• Draw these studies in the morning after avoiding all iron-containing supplements and foods for at least 24 hours to avoid falsely elevated results 1, 2

Complete Blood Count (CBC)

Order a CBC to assess for overt iron-deficiency anemia, which is a well-established secondary cause of RLS with significantly higher prevalence in affected patients. 1 The American Geriatrics Society specifically recommends CBC to identify anemia requiring more aggressive iron repletion. 1 This is particularly important since 42.3% of RLS patients without anemia still have iron deficiency. 3

Additional Required Laboratory Tests

The European Urology guidelines mandate a comprehensive metabolic workup for RLS: 1

• Electrolytes and renal function (BUN/creatinine): Essential to identify chronic kidney disease, a secondary cause of RLS with increasing prevalence 1
• Thyroid function (TSH): Part of standard endocrine screening for RLS 1
• Calcium: Included in baseline metabolic assessment 1
• HbA1c: Screens for diabetes mellitus, which has been associated with RLS and can cause peripheral neuropathy that mimics RLS 1
• Urine albumin-to-creatinine ratio: Assesses for renal disease 1

Lipid Panel Justification

Proceed with the lipid panel given her mildly elevated profile. While not directly related to RLS diagnosis, cardiovascular risk assessment is appropriate in a young adult with dyslipidemia. 4 However, this is secondary to the RLS workup priority.

Critical Diagnostic Pitfall to Avoid

Do not diagnose RLS without excluding mimics through proper examination and testing. 1 Without differential diagnosis, 16% of patients who do not have RLS will be misclassified if you only assess symptom criteria. 1 Your patient's chronic exertional compartment syndrome (CECS) could produce leg discomfort, but CECS pain:

• Occurs specifically with exertion and dissipates quickly after activity cessation 5, 6
• Does not follow the circadian pattern of RLS (worsening at night/rest) 1
• Does not improve with movement during symptoms 1

A thorough neurologic examination is essential to identify peripheral neuropathy, radiculopathy, or vascular disease as alternative diagnoses. 1 Normal exam findings with appropriate iron studies support primary RLS, while abnormal findings suggest other conditions. 1

Why These Labs Cannot Be Deferred

Women with IDNA and RLS have younger age at onset and longer disease duration compared to those with iron-deficiency anemia. 3 Your 21-year-old patient fits the high-risk demographic. Additionally:

• IDNA in women presents specific clinical features including higher risk of severe daytime tiredness/sleepiness 3
• Regular screening of peripheral iron parameters is recommended even in patients with normal blood counts for timely optimal management 3
• Iron deficiency may be severe despite normal hemoglobin levels 3

Laboratory Testing Algorithm

1. Morning fasting iron studies (ferritin + transferrin saturation) after 24-hour supplement/iron-rich food avoidance 1, 2
2. CBC to assess for anemia 1
3. Comprehensive metabolic panel (electrolytes, renal function, calcium) 1
4. TSH for thyroid screening 1
5. HbA1c for diabetes screening 1
6. Urine albumin-to-creatinine ratio 1
7. Lipid panel for cardiovascular risk assessment 4

Do not order polysomnography or periodic limb movement studies as part of routine RLS diagnosis—these are reserved for uncertain diagnoses or research settings. 1, 2