What laboratory tests should be ordered for a 17-year-old female with an 8‑lb weight loss over one year, early satiety, and no abdominal pain, diarrhea, or rectal bleeding?

Laboratory Workup for 17-Year-Old Female with Weight Loss and Early Satiety

Order a complete blood count (CBC), comprehensive metabolic panel (CMP) with electrolytes and liver/renal function, and screen for eating disorders, celiac disease, and inflammatory bowel disease as the initial laboratory assessment 1.

Core Laboratory Tests

Given the presentation of unintentional weight loss with early satiety in an adolescent female, your initial laboratory panel should include:

Essential First-Line Tests

• Complete Blood Count (CBC) - to identify anemia (particularly microcytic anemia which may indicate chronic GI blood loss or malnutrition) 1, 2
• Comprehensive Metabolic Panel - including electrolytes, liver enzymes, renal function, and albumin 1
  • Albumin is particularly important as it has 94% specificity for identifying significant pathology 3
  • Electrolyte abnormalities may suggest purging behaviors or malnutrition 1

Critical Screening Tests

• Celiac disease serology (IgA tissue transglutaminase antibodies with total IgA level) - essential screening given weight loss and early satiety 4
• Inflammatory markers: C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) 2, 3
  • CRP has 88% specificity for inflammatory conditions 3
  • The case report 2 specifically highlights how elevated inflammatory markers led to diagnosis in a similar presentation
• Fecal calprotectin - if inflammatory bowel disease is suspected, this has 99% sensitivity for IBD 3
• Thyroid function tests (TSH, free T4) - hypothyroidism can present with weight changes and GI symptoms 5

Clinical Context and Reasoning

Eating Disorder Consideration

The combination of weight loss and early satiety in a 17-year-old female raises concern for an eating disorder, particularly anorexia nervosa with restrictive behaviors 1. The APA guidelines emphasize that initial evaluation must include:

• Vital signs with orthostatic measurements (pulse and blood pressure)
• BMI calculation and comparison to previous weights
• Assessment for signs of malnutrition or purging

Critical pitfall: Even if eating disorder seems likely, do not stop at this diagnosis. The laboratory workup must still rule out organic causes 1, 6.

Organic Pathology

Early satiety without abdominal pain or GI bleeding narrows but does not eliminate serious pathology:

• Celiac disease can present with subtle symptoms and weight loss 4
• Inflammatory bowel disease may present with weight loss before overt GI symptoms develop 3
• Malignancy or structural abnormalities were ultimately found in similar presentations 2, 6

Additional Testing Based on Initial Results

If initial labs show:

• Anemia: Add iron studies, ferritin, and consider urine dipstick for hematuria (1% of IDA cases have renal malignancy) 4
• Elevated inflammatory markers: Proceed with fecal calprotectin and consider imaging 2
• Electrolyte abnormalities: Obtain ECG to assess for QTc prolongation, especially if restrictive eating or purging suspected 1
• Low albumin: Suggests significant malnutrition or protein-losing enteropathy; warrants GI evaluation 3

Important Caveats

Do not accept a functional diagnosis without completing organic workup. The case series 6 specifically warns that adolescent females with weight loss and GI symptoms may have defined gastroenterological disturbances even when eating disorders seem likely and routine diagnostics appear normal.

Urine testing for blood should be included in all patients with unexplained weight loss and anemia 4.

The absence of diarrhea or blood in stool does not exclude significant pathology - proceed with full laboratory evaluation regardless 2, 6.