Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (785 page)

   Urine confirmation assays typically target
only
THC-COOH; limit of detection/quantitation is 5–15 ng/mL

   GC/MS: selected ion -monitoring mode for quantitative analysis of serum, plasma for THC, 11-OH-THC, THC-COOH; limits of quantitation: 1–5 ng/mL.

   LC/MSn (multiple MS).

   Multiple reaction–monitoring mode for qualitative or quantitative analysis of THC, 11-OH-THC, THC-COOH

   Limits of detection/quantitation: 0.5–5 ng/mL

CARBON DIOXIDE, TOTAL

   Definition

   Total carbon dioxide consists of carbon dioxide (CO
₂
) in solution or bound to proteins, bicarbonate (HCO
₃
⁻
), carbonate (CO
₃
²⁻
), and carbonic acid (H
₂
CO
₃
). In practice, 80–90% is present as HCO
₃
⁻
and is a general guide to the body’s buffering capacity. It is usually measured with electrolytes as a panel.

   
Normal range:

   0–2 years: 20–25 mmol/L

   2–16 years: 22–28 mmol/L

   >16 years: 24–32 mmol/L

   Use

   To evaluate the total CO
₃
²⁻
buffering system in the body as well as the acid– base balance