Technical Protocols: Their Value And Impact

from the Winter 1996 issue

Many laboratory personnel who have successfully acquired accreditation have commented that one of the most significant benefits of going through the process is formalizing the policies and procedures for all aspects of laboratory operations. Up to date, detailed, accurate documents which describe how various tasks are accomplished in the laboratory serve as a formal, permanent record, and form the cornerstone upon which continuity of care can be built. Technical protocols for performing each type of vascular examination are understandably some of the most important documents for guaranteeing high quality, reproducible test results.

The examination protocols should be very detailed and explicit, and should describe step-by-step how the entire test is performed. The detail should be such that a substitute technologist could come into the laboratory and perform the examinations exactly as they are customarily done. Since every laboratory performs the examinations in a unique manner, it is important that the protocols be specific and reflective of the techniques actually used in the laboratory. It is not appropriate for vascular laboratory operations or for the purpose of accreditation to use photocopies of manufacturers' manuals, procedure manuals, or other copyrighted materials, such as journal or book chapters. Such published information may be used as guidelines, if tailored to reflect the specific examination techniques used in the laboratory. Commercially available policy and procedure manuals must also be edited to reflect the exact testing procedures used. As these manuals are generally very extensive and inclusive, only the procedures actually performed in the laboratory need to be documented.

Once the completed self study documents are submitted for accreditation, the reviewers will evaluate the technical protocols for compliance to the Standards. The second step of the review process involves comparing the case studies to the protocols, to determine whether they demonstrate adherence to the written protocols, and in turn, compliance with the Standards. A written protocol for every type of procedure must be submitted with the self study documents, with the requisite number of case studies. Failure to provide a complete set of protocols and case studies often results in deferral of the decision regarding accreditation until the missing information is submitted and evaluated by the reviewers.

The Standards comprise an indispensable guide for determining what to include in the technical protocols. Required as well as recommended characteristics are clearly delineated for both primary and secondary testing techniques for each clinical area of testing. Primary testing techniques must be provided. Secondary testing may be used in conjunction with the primary testing or for special, defined indications. An algorithm describing when secondary tests are used should be provided. The remainder of this article will focus on primary testing protocols. Additional information regarding secondary procedures may be found in the Standards.

For extracranial cerebrovascular testing, duplex ultrasonography is the primary testing technique. The technical protocol must encompass both real-time gray scale imaging (B-mode) and analysis of the angle corrected Doppler spectrum. Color Doppler imaging is considered complementary. Interrogation throughout the entire course of the cervical carotid and vertebral arteries on both sides and recording of representative measurements is required by the Standard. The protocol must also specify how the presence and extent of disease is documented. In areas of suspected stenosis, spectral Doppler measurements are made proximal, within and distal to the site of stenosis. The Doppler angle of insonation must be specified, since velocity calculations are made with knowledge of the angle between the ultrasound beam and the vessel being examined. The Standard requires that an angle of 60 degrees or less be maintained, in alignment with the walls of the vessel under interrogation. Sample volume placement, sample volume size and scan planes my also be specified in the protocol. High quality imaging is necessary, so that plaque characterization may be accomplished. This should include attempts to measure and characterize the extent of the lesions, so that accepted diagnostic criteria may be used to assess the presence and severity of abnormality. A complete technical protocol for carotid duplex ultrasonography combines both imaging and Doppler information to document the extracranial cerebrovascular circulation.

For intracranial cerebrovascular testing, transcranial Doppler sonography (TCD) is used to acquire flow velocity data with a directional pulsed Doppler instrument. Duplex color flow imaging may also be done, but is not required. The technical protocol should specify the use of appropriate anatomic acoustic windows. Each of the intracranial arteries are sampled at multiple depths, to determine the presence of focal stenosis. The acoustic intensity must be decreased when using the transorbital window. For identifying the intracranial vessels, the protocol may also specify sample volume size and depth, flow direction relative to the transducer, the angle of orientation of the transducer, and common carotid artery and other compression maneuvers. The intracranial circulation is assessed for abnormal hemodynamics and physiology by changes in flow velocity and the spectral waveform characteristics.

A variety of testing techniques may be used as primary instrumentation for peripheral arterial testing. The Standard requires measurement of systolic blood pressure at one or more levels, combined with either velocity waveform or plethysmographic analysis. As such, the technical protocol should describe either ankle brachial indices or full segmental pressure measurements. The protocol must specify how the ankle brachial indices are calculated. The size and positioning of the pneumatic cuffs must be specified in the protocol. The Standard requires comparison of the limb pressure to the contralateral paired segment, to the segments immediately above and below on the same side, and to the higher brachial systolic pressure. If treadmill exercise testing or cuff induced reactive hyperemia testing are used, a clearly defined, standardized technique should be described in the protocol.

The technique for continuous wave Doppler waveform analysis must specify insonation of the major extremity arteries and recording of the velocity waveforms. As with segmental limb air plethysmography bilateral examinations are considered essential. Standardized cuff volumes must be specified for plethysmography. There should also be some notation of the conditions which may produce waveform artifacts, to prevent misinterpretation of study results.

Arterial duplex ultrasonography may be used to provide additional information regarding the morphology of the disease process. The protocol must delineated the use of real-time gray scale imaging to document vessel anatomy and morphology of the arteries or bypass grafts. Combined with this, flow characteristics are to be documented by Doppler sampling throughout the course of each vessel segment. The Standard requires a Doppler angle of insonation of 60 degrees or less. In the presence of disease, measurements should be made proximal, within and distal to the site of stenosis. Color Doppler imaging is considered complementary. If both upper and lower extremity arterial testing is offered in the laboratory, specific protocols must be provided for each.

Duplex ultrasonography is required for venous testing. The technical protocol should specify which vessels are interrogated, the sequential nature in which the examination is performed, the intervals between compressions, and how the extent and location of disease is evaluated. The protocol should specify how venous thrombosis, venous insufficiency and valve function are evaluated. Appropriate imaging includes both transverse and longitudinal views. The hemodynamics of venous blood flow must also be evaluated by spectral Doppler waveform analysis obtained at rest and during ancillary maneuvers, such as compression, Valsalva and forced respiration. As the Standard requires spectral Doppler assessment of venous hemodynamics, color Doppler imaging may not be used alone. In addition, the Standard requires bilateral examinations. Unilateral examinations may be appropriate for specific indications, if unilateral testing is performed, the laboratory should provide a clinical algorithm for selecting patients. As in the case of arterial testing, if upper extremity venous testing is offered, a specific protocol must be provided.

For visceral vascular testing, duplex ultrasonography is required. Specific protocols for each vessel group must be supplied. The protocols should describe assessing the anatomy and physiology of the vessels in a sequential manner, so that the location and extent of disease can be documented. The techniques should include specific information regarding patient preparation and positioning, gray scale views obtained, Doppler angle of insonation, sample volume size and sites, and velocity and ratio calculations. Each visceral vascular technical protocol should specifically address how imaging and hemodynamic data are collected for evaluation of these vessel groups.

Some individuals choose to further refine their protocols, by defining the purpose of the examination, indications, contraindications and limitations of each type of examination. Resolution of differences among results from various testing modalities should also be described.

After detailed, specific technical protocols are produced for every type of examination offered in the laboratory, it is essential to ensure that the representative case studies demonstrate adherence to the protocols provided. Since the case studies are one of the most important aspects of the application for accreditation, it is essential that they demonstrate high quality testing techniques and compliance to the Standards. With well written, comprehensive protocols in place, the medical and technical staff will find themselves in an excellent position to acquire and maintain vascular laboratory accreditation.

Top of Page

Want more news?