Standard operating procedures

Kathleen P. Freeman Synlab-VPG/Exeter, Exeter Science Park, Exeter EX5 2FN, England.

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Jennifer R. Cook Idexx Laboratories Inc, Bloomfield Hills, MI 48302.

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Emma H. Hooijberg Department of Companion Animal Clinical Studies, Faculty of Veterinary Science, University of Pretoria, Hatfield 0028, South Africa.

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 BVSc, PhD

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Written SOPs are an essential part of ensuring production of accurate and reliable results in the in-clinic laboratory. Previous articles in this 5-part series summarized the overarching framework of the total quality management system, importance of quality planning, and important aspects of the facilities, training, and documentation needed for in-clinic laboratory testing. The purpose of this article is to provide information about SOPs, including their definition, purpose, and benefits; the various types of SOPs; and the headings and content commonly addressed in SOPs as relevant to in-clinic laboratories.

Definition of SOP

Standard operating procedures are defined as written documents that indicate how to perform a routine or repetitive activity.1 Many organizations rely on SOPs to help ensure consistency and quality of their products, and most modern veterinary clinics are accustomed to the use of SOPs for activities such as surgery and practice management because such SOPs are required by many veterinary hospital accreditation programs (eg, American Animal Hospital Association or Royal College of Veterinary Surgeons). Standard operating procedures are useful tools for communicating important corporate policies, government regulations for health and safety, and best practices for achieving a high standard of patient care and are therefore important to quality management for in-clinic laboratories.

Purpose and Benefits of SOPs

The purpose of SOPs in an in-clinic laboratory is to ensure consistency and quality of results. Such SOPs communicate how routine activities should be performed for preanalytic, analytic, and postanalytic phases of in-clinic laboratory testing.2 They provide a reference for both novice and experienced veterinary personnel, who must learn and then periodically review the step-by-step instructions for conducting laboratory testing. In the authors' experience, job satisfaction and knowledge, as well as the analytic accuracy and reliability of laboratory results (and in turn, level of patient care), can be improved by having an in-depth understanding of the principles and methods used in the laboratory. Standardization of testing processes can minimize the risk of errors and limits the amount of intra- and interoperator variation that may contribute to unreliable results.

Copies of SOPs should be available at laboratory workstations in paper or digital format in a way that allows appropriate personnel to easily access them. This practice can demonstrate the veterinary practice's commitment to implementation and maintenance of a quality culture that values adherence to the instructions in the documents.

Types of SOPs

The SOPs for in-clinic laboratories can be categorized according to the organization within the clinic and laboratory, such as whether the nature of the SOPs is administrative or managerial (eg, inventory procedures; ordering supplies; storing supplies, kits, and reagents; labeling; specimen retention policies; health and safety; and disposal of biohazardous and nonbiohazardous waste) or procedural (how to perform various tests or tasks within the laboratory). Alternatively, SOPs may be organized by the 3 phases of in-clinic laboratory testing (ie, preanalytic [which includes many of the administrative or managerial SOPs], analytic, and postanalytic; Table 1).2 Other categories may be needed, depending on the laboratory setup, personal philosophy of the SOP author, and general organization of the veterinary practice.

Table 1

Examples* of preanalytic, analytic, and postanalytic aspects of in-clinic laboratory testing addressed by SOPs.

Aspect, by phase Example of SOP title Example of SOP content
 Practice recommendations for various types of testing on the basis of certain conditions or situations Recommendations for first puppy visit Fecal parasite testing, deworming, and drafting of a vaccination schedule
Recommendations for initial visit for a healthy adult dog Fecal parasite testing, heartworm antigen testing, and discussion with owner about flea, tick, and heartworm prevention
Preanesthetic workup Measurement and recording of body weight and vital signs, performance of preanesthetic bloodwork, and calculation of anesthetic doses
Cat with chronic weight loss Practice-specific recommendations for minimum database, thyroid function testing, and other possible tests to be discussed with client prior to minimum database collection
Standardization of laboratory specimen collection Blood sample collection for CBC, serum biochemical analysis, and endocrine function testing Preferred site or sites of sample collection, needle size, and collection tubes given the size of patient and type of laboratory tests selected; preferred vein for routine collections in various species, food-withholding requirements, and any protocols for dynamic endocrine function testing; or preferred order for tube filling, if multiple tests are needed or multiple tube types used
 How to conduct various tests and operate the instruments in the in-clinic laboratory How to operate the XYZ hematology instrument Step-by-step instructions for operating the indicated instrument; may include appropriate QC materials for each type of testing (or this can be split out as a separate SOP)
How to conduct a urinalysis Step-by-step instructions for conducting a urinalysis
 Evaluation of results prior to reporting Flagged results Criteria indicating the need for repeated testing or immediate contact or consultation with the submitting clinician
 Routine maintenance and cleaning required for the instruments and equipment within the laboratory Routine maintenance and cleaning for the XYZ electrolyte instrument Step-by-step instructions for maintenance and cleaning of the indicated instrument or piece of equipment; may include a schedule for maintenance and cleaning to be incorporated into an instrument or equipment log indicating when this needs to be done and when it has been done
Routine cleaning for the XYZ binocular microscope
 Checking reports for errors Report verification Checks to ensure any manually transcribed results (not those electronically transferred to the practice record) are correct (may include review or read back by a second technician); method established for validating and archiving nonprintout results (eg, photographs or cosigned worksheets); or protocol for proper sample retention (eg, location and duration)
 Routine checks to ensure correct transfer of billing information Laboratory billing Protocol for ensuring that laboratory testing is correctly billed (ie, correct amount charged to the correct patient and client)

This table is not intended to include all possible topics or aspects of laboratory function that may be addressed by SOPs.

Exact instructions to be expanded on within the SOP.

Common preanalytic aspects of in-clinic laboratory testing that should be addressed by SOPs include but are not limited to the following:

  • Individual tests or test panels recommended by the veterinary practice with certain routine visits, chief complaints, or checkups for previously diagnosed conditions.

  • Specimen collection policies of the clinic (eg, standardization of the collection site, needle size, and specimen type, such as serum, plasma, or blood).

  • Patient preparation (eg, unfed or fed status or testing protocols involving a time sequence such as the low-dose dexamethasone suppression test).

  • Specimen handling after collection (eg, centrifugation, serum separation, or blood smear preparation).

  • Specimen transport to the in-clinic laboratory (eg, identities of responsible individuals and instructions for specimen submission).

  • Specimen submission to the in-clinic laboratory (eg, types of required paperwork and notification of individuals performing the tests).

Analytic aspects of in-clinic laboratory testing that are commonly addressed with SOPs may include but are not limited to the following:

  • Instructions for maintaining and operating the various pieces of equipment (eg, centrifuges, microscopes, automated instruments, and printers) within the laboratory.

  • Instructions for various types of tests available at the in-clinic laboratory (eg, serum or plasma biochemical analysis, hematologic analysis, ELISA tests, urinalysis, or fecal parasite analysis).

  • QC for various types of laboratory testing.

  • Various checks of results prior to reporting to the requesting clinician (eg, situations requiring repeated testing, criteria for immediate notification, criteria for comparative testing with the reference laboratory or clinical pathologist review, and checks to ensure that all requested tests have been completed).

In the postanalytic phase of in-clinic laboratory testing, aspects commonly addressed by SOPs may include but are not limited to the following:

  • Presentation and communication of laboratory results (eg, report format and delivery method [oral vs written]).

  • Documentation (records, printouts, or laboratory notes) and verification of laboratory test results, including having 2 laboratory workers sign off on an agreed-upon result and appropriate archiving of test results that may need to be recorded by photographing an image (such as benchtop ELISA results or a blood type card or gel).

  • Turnaround times.

  • Entry of laboratory test results into the medical record.

  • Minimum storage times of samples after analysis.

  • Billing for laboratory tests.

Items and Content Commonly Used in SOPs

Headings used in SOPs may differ slightly depending on the subject. Items and content recommended by the American Society for Veterinary Clinical Pathology are summarized for analytic SOPs that address a specific laboratory testing modality (Table 2).3 These may be modified as needed for pre- and postanalytic procedures. An example of an SOP is provided (Appendix; Supplementary Appendix S1, available at:

Table 2

Summary of recommendations of the American Society for Veterinary Clinical Pathology3 regarding items and content commonly included in SOPs for veterinary diagnostic laboratories.

Item* Contents
Title page
  • Title with an identification number and revision number as applicable.

  • Date of issue.

  • Number of pages.

  • Name of person or persons who issued or approved the SOP.

  • If a revision, original issue date and list of all revision dates and numbers.

  • Scheduled expiration or review date.

Title header and page numbers
  • Simple title header and cumulative page number repeated at the top of each page (eg, page 4 of 10, etc) to ensure that no pages are missing.

Introduction, purpose, scope, and principle of the procedure or assay
  • Introduction or purpose may be appropriate to understand the context and scientific basis of the test, what it measures, and how it is relevant to health or disease status.

  • Scope indicates the personnel or job titles that need to know this SOP.

Timing details
  • Information on the frequency or days of the week that the test or procedure is performed.

  • Expected turnaround time for results reporting.

Health and safety concerns, including handling and disposal of any hazardous materials
  • Reminder of the importance of health and safety in the workplace and best practices or legislative requirement for hazardous materials.

  • List of personal protective equipment that should be used (eg, goggles, laboratory coat, and gloves), if relevant.

Specimen requirements
  • Type of specimen (eg, serum, citrated plasma, heparinized plasma, or EDTA-treated blood).

  • Volume of specimen.

  • Rejection criteria if applicable (eg, severe hemolysis or lipemia).

Reagents, control materials, equipment, and any other needed supplies or tools
  • Names of reagents or other materials or equipment needed to complete the procedure (ie, “the ingredients list”).

Routine QC
  • Description of basic routine QC procedures, prescribed troubleshooting steps if QC results are outside of acceptable limits, and actions that should be taken once a root cause has been established.

  • Statement that if controls fail, patient samples should not be run or reported.

  • Description of actions to be taken when a system is unavailable or a procedure cannot be performed owing to mechanical failure or other reasons (eg, instructions for submitting samples to external laboratories or for storing samples until they can be tested).

  • Detailed step-by-step instructions so that a newly trained employee could run the test without asking questions (ie, “the recipe”).

Interpretation criteria
  • Any comments routinely included on a laboratory report, such as platelet clumping or interferences for thyroid hormone concentration measurement.

  • Reference intervals or reportable ranges for the test.

  • Sensitivity and specificity of the test.

  • Description of conditions that interfere with interpretation (eg, hemolysis, lipemia, icterus, anticoagulants, or medication effects).

  • Description of test limitations (eg, an initial period after infection when a serologic test result might be negative) or other reasons for test invalidation or possible error in results.

  • Formulas or equations for relevant calculations performed manually or within the laboratory software (eg, CBC differential calculations).

Reporting of results and other postanalytic concerns
  • List of names or numbers of specific records or forms that are to be used.

  • Instructions for storage or disposal of samples.

  • Instructions for archiving of associated forms or other paperwork.

Approval signoff
  • Signature and title of the person or persons who approved the SOP.

  • Any other miscellaneous notes regarding observations or troubleshooting.

  • Information regarding maintenance or other logs.

  • Package inserts.

  • Related SOPs.

  • Result recording forms or worksheets.

  • Quick reference guides.

  • Relevant scientific references.

Some of the listed content items may not be applicable to every SOP, and if this is the case, the item should remain in the document with “not applicable” noted to maintain the standardized format and thus ensure that no content is inadvertently omitted.

If desired, routine QC can be detailed in a separate SOP and referenced in the test SOP.

May be included on the title page or at the end.

Clinical Bottom Line

Standard operating procedures are an essential item for the in-clinic laboratory and one of the most important components of a quality management system. They provide a valuable reference for employees, are useful for training, and help ensure reliability, accuracy, and consistency of results produced in the in-clinic laboratory. They are a best practice contributing to a high level of patient care.

The authors hope that veterinary clinic personnel will use the information provided here to commence and enhance SOP usage. Board-certified veterinary clinical pathologists (eg, members of the American College of Veterinary Pathologists or European College of Veterinary Clinical Pathology), veterinary clinical laboratory directors, and laboratory professionals in industry, commercial diagnostic reference laboratories, and government-run diagnostic reference laboratories are available for further consultation on these matters.


No third-party funding or support was received in connection with this report or the writing or publication of the manuscript. The authors declare that there were no conflicts of interest.



Quality control


Standard operating procedure


  • 1.

    US Environmental Protection Agency. Guidance for preparing standard operating procedures (SOPs). Available at: Accessed Aug 17, 2020.

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  • 2.

    Cook JR, Hooijberg EH, Freeman KP. Quality management for in-clinic laboratories: the total quality management system and quality plan. J Am Vet Med Assoc 2021;258:5561.

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  • 3.

    Arnold JE, Camus MS, Freeman KP, et al. ASVCP guidelines: principles of quality assurance and standards for veterinary clinical pathology (version 3.0): developed by the American Society for Veterinary Clinical Pathology's (ASVCP) Quality Assurance and Laboratory Standards (QALS) Committee. Vet Clin Pathol 2019;48:542618.

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Example of a standard operating procedure (SOP) for an in-clinic laboratory.

SOP: Refractometer Specific Gravity and Total Protein Determination In-clinic Laboratory ABC Veterinary Hospital Anytown, State, USA
SOP #: 2019-2 Version: 2
Date: 10-22-2019
Original release date (if revision): Version 1 released 10-13-2018 Pages: 1 File name: 2019-2 Refractometer SG and TP.docx
Created by: John Doe Checked/Authorized by: [Authorizer signatures here] Jane Doe, Laboratory Supervisor and Dr. Scholls, DVM.
  1. Section (SOP category):

    Analytic, general

  2. Purpose/Scope:

    Description of how to measure the specific gravity (SG) of urine and body fluids and total protein (TP) concentration (or total solids) of serum, plasma, or body fluids using a refractometer. All technical staff are to be trained in this procedure. These measurements help establish the patient's hydration status and can determine states of pathologic protein loss.

  3. Test frequency:

    The test will be performed as needed per sample collection, since delayed testing can cause artifacts/false results (ideally urine is tested within 30 min of collection)

  4. Health and safety:

    Protective gloves are worn. Any samples with potential for containing bacteria should be handled with care. All areas are to be cleaned and disinfected after testing. Care should be taken when working with glass, and any broken glass vials disposed of via sharps container.

  5. Specimen:

    Urine, serum, plasma, or cavitary/lesion fluid placed in plastic sample tubes or microhematocrit capillary tubes.

  6. Equipment list:

    1. Disposable material

      1. Pasteur pipette

      2. Tissues

    2. Devices:

      1. Refractometer

  7. Quality control

    See SOP 2018-7, Refractometer Maintenance

  8. Procedure instructions:

    1. Open the cover plate of the refractometer and place a large drop of fluid on the glass surface (test plate) using a pipette (if fluid is being transferred from a test tube).

    2. If using a microhematocrit tube, the tube must be broken in the plasma area just above the interface of plasma to buffy coat, and the plasma dripped onto the glass surface. Care should be taken not to scratch the glass surface or to include pieces of glass shards in the plasma droplet (exuding fluid from the non-broken end of the tube fragment is preferred).

    3. Immediately close the cover plate and point the refractometer towards a light source.

    4. Look through the eyepiece and identify where the fluid line intersects the scales for specific gravity and total protein. The focus can be adjusted by rotating the ring around the eye piece. If the line is not clear, gently press down on the cover plate; if still unclear, add more fluid if available.

    5. Record the values for SG and/or TP on the relevant lab reporting sheet (eg, U/A, CBC, or body fluid analysis) with appropriate units for TP; record in Laboratory Information Software if applicable.

    6. Clean the fluid off the test plate and the bottom surface of the cover plate with a tissue. If suspected infectious material was analyzed, the plate should be wiped off with ethanol.

  9. Interpretation of results:

    According to the references listed below.

  10. Results/reporting and other postanalytic procedures:

    1. Results are recorded in appropriate space of the Routine U/A Report (Lab Report Form 3), CBC Report (Lab Report Form 1), or Fluid Analysis Report (Lab Report Form 4), and also into the Laboratory Information Software.

    2. Any remaining sample is stored for 48h at 4°C in the appropriately labeled sample rack, and then discarded into the laboratory biohazard container.

    3. Any remaining microhematocrit tubes and tube fragments are discarded into sharps container.

    4. Once the remainder of the urine, blood, or fluid analysis is complete, the report form is added to the medical record (paper scanned into electronic record), and the data will be stored and then archived/deleted in the appropriate time span per SOP 2016-12.

  11. Reference materials:


    1. List of Laboratory Report Forms

    2. SOP 2018-7, Refractometer Maintenance

    3. SOP 2016-12: Medical records storage, archiving, and disposal


    4. Valenciano A and Cowell RL: Cowell and Tyler's Diagnostic Cytology and Hematology of the Dog and Cat, 4th Ed, 2014

    5. Raskin R and Meyer DJ: Canine and Feline Cytology: A Colour Atlas and Interpretation Guide, 2nd Ed, 2010

    6. Sink CA and Weinstein NM: Practical Veterinary Urinalysis, 1st Ed, 2012 – Chapter 3 and 4.

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