Common Laboratory Values

Board takeaway

• Decision: First identify what decision the laboratory result affects: infection risk, bleeding risk, or medical stability.
• Defer: The AAPD table explicitly recommends deferring elective dental treatment for absolute neutrophil count (ANC) < 1,000/mm³.
• Interpretation: Its other reference ranges support interpretation; a value within range is not procedural clearance.

Compare the decisions, not just the numbers

Use the patient's history, planned procedure, laboratory-specific ranges, and medical-team plan. ANC differs from total WBC; coagulation or glycemic reference values are not stand-alone treatment rules.

Complete blood count

• Hemoglobin: 10.5–18 g/dL; reflects oxygen carriage. Low: anemia/hemorrhage; high: polycythemia.
• Hematocrit: 32–52%; cellular proportion of blood. Low: anemia/hemorrhage; high: polycythemia/dehydration.
• RBC: 4–6 million/mm³; oxygen carriage. Low: anemia/hemorrhage; high: polycythemia, cardiac or pulmonary disease.
• WBC, reflecting host defense:
  • 1–23 months: 6,000–14,000/mm³.
  • 2–9 years: 4,000–12,000/mm³.
  • 10–18 years: 4,000–10,500/mm³.
• Low WBC associations: aplastic anemia, drug toxicity, certain infections. High: inflammation, trauma, toxicity, leukemia.

Differential: absolute counts

All ranges below are cells/mm³; associations are those listed by the source.

• Neutrophils: 1,500–8,000; elevations with bacterial infection, hemorrhage, diabetic acidosis. Apply the ANC deferral threshold above.
• Lymphocytes: 1,500–3,000; associations include viral/bacterial infection, acute/chronic lymphocytic leukemia, antigen responses.
• Eosinophils: 50–250; elevations with parasitic/allergic conditions, blood dyscrasias, pernicious anemia.
• Basophils: 15–50; elevations in some blood dyscrasias.
• Monocytes: 285–500; associations include Hodgkin disease, lipid storage disease, recovery from severe infection, monocytic leukemia.

Bleeding screen

• PT: 10.1–15.9 seconds, age-related; assesses extrinsic clotting. Prolongation: liver disease, impaired vitamin K production, surgical trauma with blood loss.
• aPTT: age-related, laboratory-dependent range; assesses intrinsic clotting/factor deficiency. Prolongation associated with hemophilia A/B/C and von Willebrand disease.
• Platelets: 150,000–400,000/mm³; clotting potential. High: polycythemia, inflammation/infection, severe hemorrhage. Low: leukemia, immune thrombocytopenic purpura.
• Adult bleeding time: < 7.1 minutes; platelet quality; prolonged with thrombocytopenia.
• INR: 1 without anticoagulation; listed therapeutic range 2–3; extrinsic clotting function; rises with anticoagulant therapy.
• The table gives no platelet cutoff for dental procedures, anticoagulant adjustment instructions, or bleeding-management plan.

Urinalysis

• Volume: 1,000–2,000 mL/day; increased with diabetes mellitus/chronic nephritis. No pediatric age/weight adjustment is supplied.
• Specific gravity: 1.015–1.025; reflects tubular reabsorption/hydration. High: diabetes mellitus; low: acute nephritis, diabetes insipidus, aldosteronism.
• pH: 5.0–9.0; reflects acid-base status. Acidic associations: diabetes, acidosis, prolonged fever. Alkaline: urinary tract infection, alkalosis.
• Casts: 1–2/high-power field; source associates casts with renal tubular degeneration in cardiac failure, pregnancy, and hemoglobinuric nephrosis; does not specify cast type.

Electrolytes and markers

• Sodium: 134–143 mmol/L; elevation associated with Cushing syndrome.
• Potassium: 3.3–4.6 mmol/L; elevation associated with tissue breakdown.
• Bicarbonate: venous 22–29; arterial 21–28 mmol/L; acid-base balance.
• Chloride: 98–106 mmol/L; elevation associated with renal disease/hypertension.
• CRP: 0.08–1.58 mg/dL, age-related; rises with infection and reflects acute inflammatory response.
• Glycated hemoglobin (HbA1c): reflects average glycemia.
  • Diagnostic guidance: For diagnostic interpretation in a nonpregnant patient, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) lists normal < 5.7%, prediabetes 5.7–6.4%, and diabetes ≥ 6.5%; a second test is usually used to confirm diabetes.
  • Source: This is supplemental medical guidance.
  • AAPD boundary gap: The AAPD quick-reference table instead prints < 5.6% and >6.5%, leaving gaps at the boundaries; those printed inequalities should not be used to exclude diabetes at 6.5%.

Common board traps

Answer aloud

ANC is 800/mm³ before elective dentistry. Your decision?

An ANC of 800/mm³ indicates increased infection risk, so defer elective dental treatment. The table does not provide an urgent-care or antibiotic protocol; any urgent problem requires the appropriate medical coordination and guidance.

Does an INR of 2.5 authorize an extraction?

No. An international normalized ratio (INR) of 2.5 falls within the anticoagulant therapeutic range listed in this resource, but a therapeutic drug-monitoring range is not an extraction criterion.

• Assess the indication for anticoagulation, bleeding history, planned procedure, and the coordinated hemostatic plan; do not infer a medication change from this table.

HbA1c is exactly 6.5%. How do you interpret this sheet?

An HbA1c of 6.5% meets the diagnostic threshold listed by NIDDK for a nonpregnant patient; a second test is usually used to confirm diabetes.

• The AAPD sheet prints a strict >6.5% inequality, so it is incomplete at this boundary.
• Use the medical diagnostic guidance and arrange appropriate assessment rather than treating 6.5% as normal or using HbA1c alone to decide dental treatment.