In a 38‑year‑old woman with blood on wiping and a plasma viscosity of 1.45 cP, are these findings clinically significant given her normal vitamin B12, folate, bone profile, iron studies, liver function tests, lipid panel, thyroid function, renal function, and C‑reactive protein results?

Blood Results Are Not Clinically Significant – Rectal Bleeding Requires Direct Investigation

These blood results are reassuringly normal and do not explain the rectal bleeding; the elevated plasma viscosity (1.45 cP) is minimally above normal range and clinically insignificant in this context, requiring direct visualization of the lower gastrointestinal tract to identify the bleeding source.

Key Blood Test Interpretation

Plasma Viscosity (1.45 cP)

• Normal range is typically 1.16–1.44 cP, so this is only marginally elevated
• This minimal elevation is not clinically significant and does not suggest hyperviscosity syndrome 1
• True hyperviscosity syndrome requires plasma viscosity typically >1.8 cP with associated symptoms (headache, visual changes, bleeding) 2, 1
• Your patient has no features suggesting hyperviscosity

Iron Studies – Completely Normal

• Ferritin 157 ng/mL (13–150): Slightly elevated but excludes iron deficiency
• Transferrin saturation 32.1% (20–55%): Normal
• Iron 15.7 μmol/L (5.8–34.5): Normal
• These results definitively rule out iron deficiency anemia as a cause of bleeding 3

Vitamin B12 & Folate – Excellent

• B12 724 pg/mL (197–771): Mid-normal range
• Folate >20 ng/mL (3.0–26.8): Replete
• No evidence of megaloblastic anemia 3, 4

Complete Blood Count – Not Provided But Critical

Important caveat: You haven't provided hemoglobin, MCV, or platelet count, which are essential for evaluating bleeding 5, 3, 6. These should be checked immediately if not already done.

What Matters Clinically

The Rectal Bleeding Requires Investigation

Blood on wiping in a 38-year-old woman demands:

1. Direct visualization: Anoscopy/proctoscopy initially, then colonoscopy if indicated
2. Common causes at this age:
   • Hemorrhoids (most common)
   • Anal fissure
   • Inflammatory bowel disease
   • Colorectal polyps/neoplasia (less common at age 38 but must be excluded)

Why These Bloods Don't Help

• Normal inflammatory markers (CRP 2 mg/L) make active IBD less likely 5
• Normal albumin (45.1 g/L) and liver function exclude malabsorption or chronic disease
• Normal renal function (eGFR >90) excludes uremic bleeding
• Normal thyroid function excludes hyperthyroidism-related diarrhea/bleeding

Clinical Pitfalls to Avoid

Do not be falsely reassured by normal blood tests – most causes of rectal bleeding (hemorrhoids, fissures, early colorectal lesions) present with entirely normal laboratory investigations 7. The diagnosis is made by direct visualization, not blood work.

Do not attribute bleeding to the marginally elevated plasma viscosity – this is a red herring. Plasma viscosity of 1.45 cP does not cause bleeding; if anything, hyperviscosity causes thrombosis, not hemorrhage 1, 8.

Do not delay endoscopic evaluation – while these bloods are reassuring that she doesn't have anemia or systemic disease, they don't identify the bleeding source.

Recommended Next Steps

1. Obtain complete blood count if not already done (hemoglobin, MCV, platelets) 5, 3
2. Proceed with lower GI evaluation: Start with anoscopy/proctoscopy; advance to colonoscopy based on findings and risk factors
3. Repeat plasma viscosity is unnecessary – the current value is not clinically actionable
4. Stool studies if diarrhea is present: Consider fecal calprotectin, stool culture, C. difficile if clinically indicated 5, 7

The slightly elevated ferritin (157 ng/mL) actually suggests adequate iron stores despite ongoing bleeding, which is favorable 3, 6.