Bar Code Tracking in Histology

Specimen volumes continue to increase in both hospital and private pathology histology laboratories.  Histology laboratories must adopt new procedures and strategies for managing this increasing volume of specimens to ensure the highest quality of patient care.  Integration of new equipment and technologies for better management of all histology specimens is crucial.

Within the hospital pathology laboratory a standard protocol is to make certain to never assign consecutive accession numbers to the same tissue type.  That is, the accessioning department would accession a skin specimen, then perhaps a liver specimen, before accessioning another skin specimen.  This is the first in a long line of procedures developed to maintain specimen integrity from specimen receipt through final sign out of the report – a built in “double check” mechanism.

Private laboratories may not have this option.  Usually, the majority, if not all, of the specimens are skin tissue.  Therefore, it is the rule, rather than the exception, that there are many skin specimens accessioned consecutively.  The integration and utilization of a bar code tracking system is one method of helping to ensure 100% accuracy in specimen identification.

The first opportunity for a unique specimen checkpoint is during the accessioning of the specimen. During accessioning, a unique two dimensional (2D) bar code label is affixed to (1) the specimen requisition, (2) the specimen bottles, and (3) each specimen cassette.  When the surgical grossing process begins, the first step is to scan the 2D bar code on the requisition, the specimen bottle and the cassette.  The information must match on all three items.  If it does not, the laboratory information system (LIS) will not allow the grossing technician to continue.  This procedure insures 100% accuracy with regard to the identity of the tissue within the cassette.

When used in conjunction with a bar coding identification / tracking system, the information from standardized surgical grossing techniques can be used to help maintain specimen integrity.  During accessioning and grossing, patient and specimen information, in the form of a 2D bar code, are applied to the requisition and grossing cassette.  Tissue processing cassettes are then placed into the tissue processor.

After processing, during the embedding phase, each cassette is removed one at a time from the holding well.  The 2D bar code on the cassette is scanned, and the case information appears on the screen of the LIS.  This information includes the gross description of the specimen type, along with the number of pieces of tissue in the cassette.  Having access to this information is critically important to the embedding histologist.  The information in the LIS can be double checked against exactly what is in the cassette, with regard to number of tissue pieces and specimen type.  This step guarantees 100% accuracy of the specimen information at the embedding phase.

After the embedding is completed, the solidified blocks are taken out of the embedding molds, and any excess paraffin is removed from the block.  This step is documented by scanning the 2D bar code on the block, and indicates that the blocks are now on a cold tray, in a refrigerator, waiting for microtomy.

The microtomy phase begins when a histologist removes a cold tray, containing blocks, from the refrigerator and takes it to their microtomy work station.  The microtomy work station is standardized, and each histologist must follow the block cutting procedure exactly.  Workflow is unidirectional; a block designated for cutting moves in only one direction, into and out of the microtome cutting area.  In addition to the unidirectional workflow, the only labelled slides present in the work envelope are those for the block that is being cut.

Scanning the 2D bar code on the block time stamps the block as being “cut”.  It also provides the histologist with the case information in the LIS, which is used to generate a unique slide label. The scans in the microtomy phase provide two additional check points to ensure specimen integrity, and “one piece’ work flow.

The block is cut into paraffin sections which are picked up on the corresponding microscope slide.  Once a block is cut, it moves into the “block done” box – never back to the “block to be cut” area.  The slides are placed into the “slides done” rack and moved into the oven for heating in order to remove water and melt the paraffin, thereby attaching the sections to the slides.  When this microtomy procedure is followed, it ensures 100% accuracy with regard to the cut tissue matching the slide label information.  Accidental “switching” of slides is not possible.  The block is now logged as being “cut” in the LIS system.

Racks of mounted and baked slides for routine hematoxylin and eosin (H&E) staining are brought to the H&E slide staining area.  After staining and coverslipping, each slide is visually inspected and checked against the corresponding block to provide a final check on specimen accuracy.  The 2D bar code on the slide is scanned to indicate “slide checked”.  Additionally, slides are checked for H&E stain quality, and the results documented on a log sheet.  Specifically, nuclei must appear blue with chromatin material visible, with eosin staining in the cytoplasm resulting in three shades of pink. The slides can now be brought to the office area for interpretation by the pathologist.

In summary, constant vigilance is required in the histology laboratory in order to guarantee specimen integrity.  This vigilance can be enhanced to a greater degree by using a bar code tracking system.  This Bar code tracking technology is recommended by the College of American Pathologists and the National Society for Histotechnology (4). In combination, bar code tracking and human diligence can result in an increase in patient care quality – a goal that all laboratorians should strive for.


  1. Theory and Practice of Histological Techniques. Chapter 10.  JD Bancroft, A Stevens ed.  Churchill Livingstone, NY.  Fourth edition. 1996
  2. Theory and Practice of Histotechnology.  Chapter 9.   DC Sheehan, BB Hrapchak.  CV Mosby Company, St. Louis. First edition. 1980.
  3. Chapman CM: Barcoding and Dermatopathology.  Advance for Medical Laboratory Professionals: Vol. 23 No 9, May 9, 2011.
  4. Brown et al.  Uniform Labeling of Blocks and Slides in Surgical Pathology.  Guideline from the College of American Pathologists Pathology and Laboratory Quality Center and the National Society for Histotechnology.  Arch Pathol Lab Med.  Accepted for publication March 12, 2015.