Editors: Olga Pozdnyakova, MD, PhD, Geoffrey Wool, MD, PhD, David Bernard, MD, PhD & Raul S. Gonzalez, MD
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Q.Our laboratory is considering adding whole slide imaging to our surgical pathology case workflow. The quality of the slides can have a negative impact on the scanning of the histologic sections. How can our histology laboratory produce histologic preparations that are optimal for whole slide imaging scanning?
A. May 2025—Thank you for highlighting the importance of glass slide quality in the digital pathology workflow. Implementing whole slide imaging workflows presents challenges for histology laboratories in their traditional practice. Achieving optimal whole slide image quality requires special attention, starting with grossing and continuing through each step of the histology preparation workflow.
To support laboratories in this endeavor, the CAP/NSH Histotechnology and CAP Digital and Computational Pathology committees have developed a resource titled “Practical Tips to Assist Implementation of Whole Slide Imaging.” This step-by-step guide provides key recommendations for grossing, tissue processing, and slide preparation to ensure optimal results when preparing glass slides for whole slide imaging. By following these recommendations, laboratories can ensure their glass slides are optimized for image capture by automated WSI. Of note, while the quality of the WSI is directly tied to the quality of the corresponding glass slide, not all “perfect” glass slides are suited for WSI.
Use of the CAP guide helps labs achieve histologic preparations of the highest quality that are optimized for WSI. You can access this resource at https://bit.ly/CAP_tipsWSI.
Humberto Trejo Bittar, MD
Associate Member, Thoracic Pathology
Director of Autopsy Service
Department of Pathology
Moffitt Cancer Center
Associate Professor
Department of Oncologic Sciences
University of South Florida
Tampa, Fla.
Chair, CAP/NSH
Histotechnology Committee
Marilyn Bui, MD, PhD
Senior Member and Professor of Pathology
Scientific Director of Analytic
Microscopy Core
Moffitt Cancer Center
Tampa, Fla.
Chair, CAP Digital and Computational Pathology Committee
Q. Are there biological reference intervals for spot urine values for creatinine, protein, microalbumin, sodium, potassium, and calcium? Some reagent manufacturers give reference intervals for spot urine tests. Is this necessary?
A. Aliquots of 24-hour urine collections are commonly used to measure renal excretion of endogenous substances. However, the concentrations of such substances in urine can vary depending on many factors, such as time of specimen collection and patient diet, physical activity, and fluid intake. A major drawback is inaccuracy in sampling. While normalizing analyte concentrations to urinary creatinine helps for some biomarkers, it does not apply to all. Furthermore, the challenge of obtaining sufficient samples for accurate reference intervals complicates the diagnostic use of parameters from 24-hour urine collections.1
Biological reference intervals for spot urine values of creatinine, protein, microalbumin, sodium, potassium, and calcium vary depending on the population, collection method, and analytical method. For creatinine, spot urine creatinine-to-osmolality ratios provide a practical approach, with studies suggesting an interval of approximately 0.08–0.19 mg/mg across adult populations, adjusting for factors like body weight and ethnicity.2 Protein and albumin in spot urine are often evaluated using creatinine-normalized ratios, highlighting gender-specific differences due to variations in muscle mass. Sodium and potassium reference intervals are stratified based on diet and regional factors. Calcium levels show variation tied to dietary intake and renal excretion efficiency. Large-scale studies, including those that use data from the National Health and Nutrition Examination Survey, provide comprehensive intervals for 24 laboratory parameters, offering detailed partitions by age, sex, and biological covariates in 24-hour urine collections.1
While reagent manufacturers may provide reference intervals, laboratories are responsible for verifying the accuracy of those intervals or establishing their own if, for example, the latter are requested by providers.
- Curcio R, Stettler H, Suter PM, et al. Reference intervals for 24 laboratory parameters determined in 24-hour urine collections. Clin Chem Lab Med. 2016;54(1):105–116.
- Hsu SP, Chien CT. Reference intervals of spot urine creatinine-to-osmolality ratio as a surrogate of urinary creatinine excretion rate. Dis Markers. 2022;2022:3549047.
Hoda Hagrass, MD, PhD
Assistant Professor of Pathology
Medical Director of Clinical Chemistry and Immunology
University of Arkansas for Medical Sciences
Little Rock, Ark.
Member, CAP Clinical Chemistry Committee