This section provides general information and recommendations for collecting specimens involving the following conditions:

• 24-hour Urine Sampling
  The excretion of any analyte in urine is not uniform throughout the 24-hour day.  Virtually every substance has a diurnal cycle, so the mass-per-time rate is not constant.  If a constant volume of urine is removed from each collection, and the remainders pooled, the analysis of the remainder will not reflect the summation of the contributions from each individual collection because the rate of excretion changes.Read more...

• Creatinine Clearance on Short Internal Collections
  One cannot perform a creatinine clearance on a truly random urine specimen since time is an important factor in the calculation. One can use a time period other than 24 hours, however. Four and 12 hour clearances are sometimes used, but any carefully timed interval can, theoretically, be used.Read more...

• Drug Interference in Specimens
  Knowledge of human biochemistry at the molecular level has long been used as a basis for rational drug design. Constructs of small molecules, peptides, and nucleic acid sequences are commonly based on the supposition that the closer they mimic or complement a naturally occurring structure, the higher the potency is likely to be and the lower the incidence of adverse safety effects.Read more...

• Water Consumption During Fasting
  There are certainly situations under which the patient can be allowed to drink more water, and in general, the one glass restriction is a guideline, not an absolute.Read more...

Note: Full articles are reserved for registered clients with sponsor level status.