Q & A Column, 5/14

• Neutrophils 0.80 × 109/L(1.8–6.8 × 109/L)
• Lymphocytes 1.00 × 109/L(1.0–3.4 × 109/L)
• Monocytes 0.20 × 109/L(0.2–0.8 × 109/L)
• Eosinophils 0.00 × 109/L(0.0–0.4 × 109/L)
• Basophils 0.00 × 109/L(0.0–0.1 × 109/L)

Now we can easily recognize that the patient has a moderate neutropenia and may be at risk of infection. In addition, we now focus our diagnostic considerations on the causes of neutropenia. We also recognize that the patient does not have a true lymphocytosis, as the absolute lymphocyte count is at the lower end of the reference range.

[/box]

 

1. Etzell JE. For WBC differentials, report in absolute numbers. CAP TODAY 2010. March;24(3):12.
2. Richardson-Jones A, Twedt D, Hellman R. Absolute versus proportional differential leukocyte counts. Clin Lab Haematol 1995;17(2):115–123.

Joan E. Etzell, MD
Medical Director, Sutter Health Shared Laboratory, Livermore, Calif.
Clinical Professor of Laboratory Medicine, UCSF School of Medicine
Chair, CAP Hematology/Clinical Microscopy Resource Committee

[hr]

Q. I work in an 800-bed university hospital core lab. My question is about the processing of 24-hour urines. We get so many per day that the jugs have become difficult to manage. When a test needs acidification, our lab assistants aliquot all tests that do not need any additive. To the remaining urine, they add 25 mL of 1 N HCl (remaining volume must be > 500 mL), mix it up, and aliquot into a sample tube. This tube is set aside for one hour for equilibration before testing is performed. The jug is then discarded. Is this an acceptable practice? In the past, we left the jug for one hour after acidification before aliquoting into a sample tube. But the process is messy and hard to manage.

A. Urine samples may be aliquoted and frozen for analysis at a later time, but to prevent specimen degradation as a consequence of repeated freeze-thawing, the urine sample should be frozen in aliquots.1 For urine samples that do not require acidification, the urine may be aliquoted and frozen, and the excess discarded. It is important to check for adequate acidification of the entire urine specimen before the aliquoting process, especially for amino acid evaluation (pH ≤ 3.0) and for catecholamines, vanillylmandelic acid (VMA), and 5-hydroxyindoleacetic acid (5-HIAA) (pH 1.0–2.0).1 After verification of adequate acidification, the aliquots can be saved and the excess urine discarded.

Recently, the Mayo Clinic Department of Laboratory Medicine and Pathology initiated a urine collection study to determine the stability of analytes under different preservatives and temperature conditions. Mayo Clinic suggests that 30 mL of 6 N HCl be added per 24-hour collection.2 See the Mayo urine preservatives chart for details.2

1. Henry JD, ed. Clinical Diagnosis and Management by Laboratory Methods. 20th ed. Philadelphia: W.B. Saunders; 2001.

2. mayomedicallaboratories.com/it-mmlfiles/Urine_Preservatives10.pdf

Gifford Lum, MD
Associate Chief, Clinical Pathology Pathology and Laboratory Medicine Service
VA Boston Healthcare System, Former member, CAP Chemistry Resource Committee

[hr]

Dr. Kiechle is medical director of clini­cal pathology, Memorial Healthcare, Hollywood, Fla. Use the reader service card to submit your inquiries, or address them to Sherrie Rice, CAP TODAY, 325 Wau­ke­gan Road, Northfield, IL 60093; srice@cap.org.