Chapter 24: Hospital and Laboratory Use |
Summary: The adoption of Code 39 in healthcare settings during the early 1980s marked a pivotal shift from manual data entry to automated, error-resistant patient and specimen tracking. The symbology's unique technical characteristics---its self-checking property, alphanumeric capability, and lack of a mandatory check digit---made it ideally suited for the demanding environments of hospitals and clinical laboratories, where data integrity is paramount and the ability to encode letters alongside numbers was non-negotiable. |
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Introduction: The Critical Need for Accuracy |
In the early 1980s, the healthcare industry faced a silent crisis: errors in patient identification, specimen labeling, and medication administration were alarmingly common, leading to misdiagnoses, incorrect treatments, and even fatalities. Before the widespread adoption of barcodes, hospitals relied on manual transcription---nurses writing patient IDs on wristbands, lab technicians handwriting labels on specimen tubes, pharmacists typing medication labels on typewriters. Each of these manual steps introduced opportunities for human error. A single digit written incorrectly could send a blood sample to the wrong patient's file, or worse, administer a drug to the wrong person. |
The industry recognized that it needed a reliable, automated method to ensure that the 'Five Rights' of medication administration were being met: the right patient, the right drug, the right dose, the right route, and the right time. This required a system that could bridge the physical world of patients, specimens, and medications with the digital world of electronic health records and laboratory information systems. |
Barcode technology, already gaining traction in the retail sector with the Universal Product Code (UPC), seemed like a natural solution. However, the UPC had a fatal flaw for healthcare applications: it was numeric-only. Hospital systems needed to encode alphanumeric data---patient initials, lot numbers, test codes, and department identifiers. When Intermec's Code 39 symbology emerged as a standard, it offered exactly what healthcare needed: the ability to encode both letters and numbers in a scannable format . |
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Code 39 Fundamentals and Healthcare Suitability |
To understand why Code 39 became so deeply entrenched in healthcare, one must understand its basic technical architecture. Code 39, also known as Code 3 of 9, was developed in 1974 by Dr. David Allais and Ray Stevens . Each character in the symbology is encoded using nine elements: five bars and four spaces. Three of these nine elements are wide, and six are narrow . This 'three of nine' pattern is why it earned its name. The scheme encodes 43 characters, including the uppercase letters A through Z, the digits 0 through 9, and a limited set of special characters such as dash, period, dollar sign, slash, plus, percent, and space . The start and stop characters are both represented by an asterisk (*) . |
One of the most significant features for healthcare was the self-checking property of Code 39. This means that if a single bar is misread due to a printing defect or smudge, it will not convert one valid character into another valid character; it will simply be recognized as an invalid pattern, and the scanner will reject the read . While this is not a replacement for a formal check digit (though many applications added a Modulo 43 check digit for extra safety), it provides a high degree of reading reliability, which is critical when dealing with patient safety . In the messy, unpredictable conditions of a hospital floor---where wristbands get wet and labels get scuffed---this self-checking robustness was a major selling point. |
Furthermore, Code 39 does not require a mandatory check digit . This made it exceptionally easy to implement. In the early 1980s, printing barcodes was not as simple as it is today. By adding a Code 39 barcode font to an existing printer, hospitals and labs could immediately start printing scannable labels without needing to purchase expensive new hardware or complex check-digit calculation software . This ease of integration accelerated its adoption. |
However, the adoption of Code 39 was not without its compromises. The symbology is widely known to have a 'low data density' . Because it requires a wide/narrow pattern to represent each character, the resulting barcode is roughly 30% to 40% wider than a Code 128 barcode encoding the same data . This means that Code 39 labels can be quite large, which is a disadvantage for small specimen tubes or tiny medication vials. This limitation would later lead to the adoption of other symbologies like Code 128 and Data Matrix in specific areas, but for the majority of the 1980s and 1990s, Code 39 was the workhorse of hospital data capture . |
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The Specimen Tube Revolution |
The Challenge of the Clinical Lab |
Before Code 39, clinical laboratories were often chaotic places. A phlebotomist would draw a patient's blood, write the patient's name and medical record number on a tube with a marker, and send it to the lab. At the lab, technicians would manually log the tube into the system, often re-typing the information. This was slow and error-prone. If the handwriting was illegible, the technician would have to track down the phlebotomist or discard the specimen. |
The introduction of Code 39 labels for specimen tubes solved these issues. At the patient's bedside, the phlebotomist would scan the patient's wristband and print a Code 39 label for the tube directly . This label contained a unique accession number that linked the physical tube to the patient's electronic record. When the tube arrived at the lab, scanners would read the Code 39 barcode, automatically log the sample into the Laboratory Information System (LIS), and route it to the correct testing station . |
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Technical Considerations for Tube Labeling |
The choice of Code 39 for specimen tubes was heavily influenced by the environment of the laboratory. Tubes are small, often round, and subject to temperature variations and chemical spills. Using Code 39 presented several technical hurdles that had to be managed. |
First, there was the issue of the curved surface. A barcode printed on a flat label and then wrapped around a cylindrical tube can become distorted. Scanners need to be forgiving of this distortion. Code 39's discrete nature---where each character is separated by an inter-character gap---made it relatively tolerant of this kind of distortion compared to continuous symbologies where the bars run together . |
Second, the low data density of Code 39 meant that labels could only hold a limited amount of information. To fit a long accession number on a small tube, the label had to be printed with the narrowest possible bars (referred to as the X dimension). Typically, this was around 0.0075 inches, which required high-quality thermal transfer printers . |
Third, the readability of damaged barcodes was crucial. In a busy clinical lab, tubes get dropped, liquids get spilled, and labels get smudged. The self-checking property of Code 39 helped mitigate this risk. As one case study in a clinical diagnostics system noted, the scanner chosen for the lab needed a 'robust read rate capable of reading even poorly printed and damaged bar codes' . Because Code 39 was widely used, the scanners were optimized for it, often achieving high read rates despite wear and tear. |
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The Patient Wristband |
Identification and the Chain of Command |
Patient wristbands are arguably the most critical application of barcodes in the hospital environment. They are the physical link between the patient and their electronic health record. In the 1980s, hospitals began using Code 39 on wristbands to ensure that the patient at the bedside was the same patient being treated in the system . |
The workflow is simple but profound. When a patient is admitted, the admissions system prints a wristband with a Code 39 barcode encoding a unique patient identifier (usually a medical record number or encounter number). The patient is then assigned to a room, and the wristband is placed on the patient's wrist. Before administering any medication, performing a procedure, or drawing blood, the nurse must scan the wristband. The scanner reads the Code 39 barcode and pulls up the patient's information on the screen, verifying their identity . |
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Adapting Code 39 for Wearable Durability |
This application posed unique challenges for Code 39. A wristband is subjected to significant abuse. It must survive hand washing, showering, exposure to bodily fluids, and general wear and tear over the course of a hospital stay . |
The width-to-narrow ratio of Code 39---typically a ratio of 2:1 to 3:1 between wide and narrow bars---is a key factor in its durability . If a wristband gets scratched, the wide bars are less likely to be completely obliterated. Furthermore, the self-checking property ensures that a scratch that makes one bar wide will likely result in an unreadable character rather than a misread one, prompting the nurse to scan again or replace the wristband. |
However, the low density of Code 39 became a serious limitation here as well. A wristband only has so much real estate. If the data string is long, the barcode wraps around the wrist, which is difficult to scan. To mitigate this, hospitals often had to use barcode fonts with a narrow X dimension or encode only a short identifier (like an encounter number) and let the system look up the rest of the data . Later, other symbologies like Code 128 and Data Matrix offered higher density and smaller footprints, but Code 39 remained the standard for many years due to existing infrastructure. |
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Medication Administration: The 'Five Rights' Enforced |
One of the most significant clinical applications enabled by Code 39 was the electronic medication administration record (eMAR). In the manual system, a nurse would look at a paper chart, take a drug from a shelf, and check the patient's paper wristband. The eMAR system changed this. When a doctor prescribed a medication, the order went into the system. At the time for administration, the nurse would scan the Code 39 barcode on the patient's wristband, then scan the Code 39 barcode on the medication label. |
If the patient was not supposed to receive that drug, or if the dosage was wrong, or if the time was wrong, the system would sound an alarm. This system required that the medication labels themselves be printed with Code 39 barcodes . This created a closed-loop system that dramatically reduced medication errors. The alphanumeric capability of Code 39 was vital here, as medication labels often contain letters (e.g., 'INSULIN' or 'MORPHINE') alongside numbers . |
The 'do-it-yourself' nature of Code 39 was also a boon for hospital pharmacies. In many hospitals, drugs arrive from the manufacturer in bulk packaging without a standardized barcode readable by the hospital's system. Pharmacists could generate a Code 39 label in-house, using a simple barcode font, and affix it to the unit-dose packaging . This was far cheaper and easier than setting up complex re-labeling machinery. |
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The Health Industry Bar Code (HIBC) Standard |
The widespread use of Code 39 in healthcare eventually led to the development of the Health Industry Bar Code (HIBC) standard, managed by the Health Industry Business Communications Council (HIBCC) . While other symbologies like Code 128 and Data Matrix are now permitted, the HIBC standard was initially rooted in Code 39 . |
The HIBC standard specifies how to encode various pieces of information---such as the labeler identification code, product number, lot number, expiration date, and serial number---into a Code 39 barcode . This standardization was essential for supply chain management. It ensured that a medical device manufactured in one state could be scanned and tracked by a hospital in another state, with both systems understanding the data format . |
The standard takes advantage of Code 39's ability to encode spaces and special characters like the slash (/) and plus (+) to separate data fields, creating a structured syntax that can be parsed by software . This made the barcode not just a tracking number, but a rich data carrier that could convey complex supply chain information. |
However, the adoption of HIBC also highlighted Code 39's technical limitations. Because the HIBC data string could be quite long, the resulting Code 39 barcode could become unwieldy and difficult to fit on small packages. As a result, the HIBC standard now permits the use of more modern 2D symbologies like Data Matrix, which can pack far more data into a smaller space . Nonetheless, Code 39 remains a cornerstone of the HIBC standard for simple, alphanumeric applications. |
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Laboratory Information Systems (LIS) and Automation |
Clinical laboratories are heavily automated, with conveyor belts, robotic arms, and high-speed analyzers. Code 39 has been integral to this automation since the 1980s . In an automated lab, specimen tubes are loaded into carriers and sent along a conveyor system. At various points along the conveyor, scanners read the Code 39 labels on the tubes . |
One of the key technical features of Code 39 that made it suitable for this automated environment is its discrete, variable-length nature . Because it is discrete, a scanner can easily pick out where one character ends and another begins, even if the barcode is slightly damaged. Because it is variable length, the system can encode an accession number that is 8 digits long or 14 digits long, depending on the hospital's needs, without any change to the system architecture. |
Furthermore, the fact that Code 39 does not require a check digit in the standard made it less computationally intensive for early microprocessors to decode. In the 1980s and 1990s, processing power was a premium in embedded systems. The simple logic required to decode Code 39 was a major advantage over more complex symbologies . Even with the optional Modulo 43 check digit, the calculation is relatively simple. A hospital in China, implementing a laboratory system in 2006, specifically noted using 'CODE39 plus check digit (MOD46)' because it was compatible with their Hospital Information System, Laboratory Information System, and most detection instruments . This cross-compatibility between systems (HIS, LIS, and analyzers) was a major driver for adopting Code 39. It created an ecosystem where the same scanner could read wristbands, tube labels, and instrument status codes without reconfiguration. |
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Military and Government Influence |
It is impossible to discuss the adoption of Code 39 in hospitals without acknowledging the influence of the United States Department of Defense (DoD). In 1982, the DoD adopted Code 39 for its LOGMARS (Logistics Applications of Automated Marking and Reading Symbols) system under MIL-STD-1189 . This standard required all government property to be marked with Code 39 barcodes . |
Because so many hospitals are affiliated with or receive funding from the Department of Veterans Affairs and other military entities, the LOGMARS standard bled into civilian healthcare. Manufacturers of medical supplies and pharmaceuticals who contracted with the government were compelled to adopt Code 39 for their labeling . Consequently, the scanners and printers used in military logistics were compatible with those used in hospitals. This was less of a technical decision and more of an ecosystem lock-in, but it proved highly effective at standardizing barcode technology across the entire healthcare supply chain. The government's insistence on the optional Modulo 43 check digit for these applications also forced the industry to adopt more robust error-checking practices than the base Code 39 standard required . |
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The Challenge of Damaged Labels and 'Squint' Reading |
One of the most significant technical concerns in the hospital environment is the degradation of barcode quality. A lab specimen tube might get washed with a harsh solvent. A patient wristband might be soaked in water. A medication label might be torn. Code 39 was well-suited to this environment because of its generous tolerances. |
The specification for Code 39 allows the width ratio between narrow and wide elements to be anywhere from 1:2 to 1:3 . This flexibility means that if the printing process is not perfectly calibrated, the barcode will still likely be readable. Additionally, the inter-character gap---the space between characters---is not data-bearing. This means that some distortion is allowed between characters without corrupting the data. |
However, this robustness has a limit. Clinicians often refer to the need for a scanner with a 'squint' capability---the ability to read a barcode even if it is partially obscured. Because Code 39 is linear and discrete, if a section of the barcode is damaged, the scanner can often still read the characters on either side of the damage, or it will at least detect that the read is invalid, prompting a rescan . In cases where the label is completely destroyed, the system rejects the scan, preventing a misidentification. This feature is a critical point of patient safety, ensuring that 'the machine' catches the error that a human might miss. |
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Conclusion: An Enduring Legacy |
The adoption of Code 39 in hospitals and laboratories in the early 1980s was one of the most successful applications of barcode technology in history. It transformed patient care by automating the verification of the 'Five Rights,' virtually eliminating a generation of medication errors. It revolutionized the clinical laboratory by turning specimen tracking from a manual, error-prone process into an automated, efficient, and traceable system. |
The specific technical features of Code 39---its self-checking ability, its alphanumeric capability, its tolerance for damage and printing errors, its lack of a mandatory check digit, and its discrete, variable-length encoding---all aligned perfectly with the needs of the healthcare environment. The self-checking property provided a layer of safety against misreads that was crucial for life-and-death situations . The alphanumeric capability allowed for the encoding of complex medical data that simple numeric barcodes could not handle . The lack of a mandatory check digit meant it could be adopted quickly and cheaply using existing printers . |
Despite its drawbacks---notably, its low data density, which made it difficult to fit complex data on small labels---Code 39 became the *lingua franca* of healthcare barcoding for two decades. Even as newer, more dense symbologies like Code 128 and Data Matrix entered the scene, Code 39 remained an embedded standard. The HIBC system still accommodates it . Many legacy systems were built around it. |
Today, one might argue that Code 39 is 'retired' in some high-tech hospital settings, replaced by 2D barcodes that can encode entire paragraphs of data. But it is important to recognize that in the vast majority of hospitals around the world, you will still find it. You will see it on that vial of insulin, on the wristband of a patient, and on the label of a blood sample. Its simplicity is its strength. Code 39 may be less dense and less glamorous than its successors, but it is the foundation upon which modern hospital informatics was built. It provided the crucial first step from paper to digital in the most human of environments: the care of the sick. |
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Detailed Summary |
This chapter has explored the profound and lasting impact of Code 39 on the hospital and clinical laboratory environment. We have seen how a symbology designed for general logistics found its true calling in the high-stakes world of patient safety and specimen integrity. |
The Critical Need: Before Code 39, manual transcription of patient and specimen data was the standard, leading to an unacceptably high rate of medical errors. The need for an automated system that could ensure the 'Five Rights' of medication administration and provide positive patient identification drove the industry toward barcode technology. The standard UPC, however, was numeric-only and insufficient for healthcare's alphanumeric needs, paving the way for Code 39 . |
The Technical Fit: Code 39's technical profile was uniquely suited to the healthcare environment. Its self-checking property ensured that printing defects or physical damage to labels would not cause one character to be misread as another, dramatically reducing scan errors . Its alphanumeric capability allowed it to encode patient initials, drug names (as letters), lot numbers, and test codes, making it far more versatile than numeric-only symbologies . Its lack of a mandatory check digit and variable-length encoding meant it could be easily integrated into existing hospital printing systems with a simple barcode font, accelerating adoption without the need for complex new hardware or software . |
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The Applications: |
1. Specimen Tubes: Code 39 labels transformed the clinical lab. A unique patient identifier printed on a tube label could be scanned to log the specimen into the Laboratory Information System (LIS), track it through automated analyzers on conveyor belts, and link test results back to the correct electronic health record . The symbology's tolerance for damage and its readability on curved surfaces were critical here . |
2. Patient Wristbands: Code 39 became the standard for patient identification, providing a physical link between the patient and their digital record. Scans at every clinical touchpoint---medication administration, blood draws, surgery---verified the patient's identity. The wristbands had to survive harsh conditions, and Code 39's robust wide/narrow ratio and self-checking design made it reliable even when wet or scratched . |
3. Medication Labels: Pharmacies adopted Code 39 to create unit-dose labels. This enabled the eMAR (electronic Medication Administration Record) system, where scanning the patient's wristband and the medication label ensures the right drug is given to the right patient at the right dose and time . |
4. The HIBC Standard: The Health Industry Bar Code standard formalized the use of Code 39 for healthcare supply chains, enabling consistent tracking of medical devices and pharmaceuticals from manufacturer to patient. While Code 39 is still included in the standard, the use of 2D codes is now recommended for higher data density needs . |
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The Drawbacks: The primary drawback of Code 39 is its low data density. It is typically 30% to 40% wider than a Code 128 barcode encoding the same data . This made it difficult to fit long data strings on small items like patient wristbands or tiny specimen tubes. This limitation eventually led to the adoption of Code 128 and Data Matrix for space-constrained applications . |
The Legacy: Despite being technically surpassed in some areas, Code 39 remains a deeply embedded standard in healthcare. Its self-checking nature provided a critical safety margin that influenced the design of all subsequent healthcare barcode standards. It was the symbology that proved barcoding could save lives, and its influence is still felt in the medical systems of today. It is a testament to how a well-engineered, simple, and robust technology can have a lasting and positive impact on human life. |
cs@easiersoft.com