Issues of reliability and validity

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Chapter contents

4.1 Pulse diagnosis and the need for clear and unambiguous terminology 34
4.2 Pulse diagnosis, subjectivity and the need for reliable assessment methods 37
4.3 Pulse in changing contexts 38
4.4 The normal pulse 38
4.5 Reliability and validity of the pulse diagnosis process 39
4.6 Radial pulse palpation method 42
In their guidelines for providers of CM education, the World Health Organization (WHO 1999) regarded pulse diagnosis as a core component of the CM diagnostic framework and integral to the curriculum of quality degree programs in acupuncture and Chinese herbal medicine. This view is similarly reflected in curriculum guidelines by accreditation and regulation authorities in various countries (BAC 2000, BMA 2000, NASC 2001). These recommendations are largely founded on the premise that pulse assessment is a clinically reliable diagnostic technique. The antiquity of the use of the technique and historical roots are seen as proof of this; if a technique has been in use for so long, then who is to question the practice of pulse diagnosis? Unfortunately, a ready acceptance of what is written in the classics and contemporary texts, combined with the diversity of CM practices, means the pedagogical framework for using pulse diagnostically is readily compromised, so questioning its reliability for this task (Birch 1998, Hammer 2001, King et al 2002, Wiseman & Ye 1999).
At the core of this problem is the actual nature of pulse diagnosis: it is dependent first and foremost on touch. Consequently, the literature and descriptions of the pulse qualities are enshrouded by tactile imagery constructed from a range of literary devices including analogies, similes and metaphors. For example, Wang Shu-he describes the Tight pulse (Jiu/Jing Mai) as being ‘an inflexible pulse like a tensely drawn rope’ (1997: p. 3). At times, writing involved prose as a learning aid. Notably, Li Shi-Zhen’s Bin Hue Mai Xue is written entirely in rhyming format. Yet it is this very use of descriptive imagery that makes pulse diagnosis a doubly difficult technique to apply in a clinical context. Not only is pulse diagnosis dependent on an individual’s perception of touch, but there are no clear and unambiguous guidelines for interpreting these literary images in a practical sense.
4.1. Pulse diagnosis and the need for clear and unambiguous terminology
Formulating terminology to describe the different pulse types only happened after implementation of pulse in the CM diagnosis process itself (Wiseman and Ye 1999). Originally, pulses were defined descriptively, often using metaphors with particular relevance to everyday life at the time of their development. For example:
When man is sick the pulse of the liver moves more fully, and it is large and long and slightly tense, felt on both light and heavy pressure; but it is also slippery like the sound of many long bamboo rods strung together, then one can speak of a sick liver.
At the point of death the pulse of the liver moves with increased speed and strength, like a new long bow of a musical instrument — and then one can speak of the death of the liver.
When man is tranquil and healthy the pulse of the spleen flows softly, coming together and falling apart like a chicken treading the earth — and then one can speak of a healthy spleen
Yet, despite recognition of the need for more detailed and informative definitions of pulse qualities as undertaken in Mai Jing, the old descriptive terms remained in subsequent writings. For example, in his classic text on pulse diagnosis, Li Shi-zhen describes the Rough (choppy) pulse (Sè mài) with descriptive terms in addition to more informative details from the Mai Jing:
Fine and slow, going and coming difficult, short and scattered.
Possibly one stop and again comes [description from the Mai Jing].
Uneven, not regular [description from the Su Wen].
Like a light knife scraping bamboo [description from the Mai Jue (Pulse Knacks)].
Like rain wetting sand.
Like a diseased silkworm eating a leaf.
Wiseman and Ye (1999) note interpreting pulse qualities is not helped by complications arising from authors over the centuries attempting to expand and further define the pulse types listed in older CM texts and adding their own interpretations while doing so. A further complicating factor with the use of pulse terminology derived from a different cultural context, and indeed, a temporal context as well, is that it is difficult to determine the exact definition and context of the original author’s use of a pulse word or term. Agdal (2005) notes the ‘Language is not a neutral tool describing realities but is embedded with cultural meaning; it is a formative principle which constitutes objects as much as it describes them’ (p. S-68). According to Manaka, Itaya and Birch (1995) this problem is further accentuated when authors do not reference the sources from which they obtained the pulse terminology used, so negating the benefits of a standard system of terminology.
Confusion also arises when terminology is used in a descriptive manner but also to identify specific CM pulse qualities. The Replete pulse is a good example of this dichotomy. The term ‘replete’ is often used in the CM literature to convey the idea of excess, and thus is used as a general descriptor of any pulse that hits the finger with considerable strength on palpation. However, the term is also used to name one of the specific CM pulse types, the Replete pulse (Shí mài), traditionally meaning a pulse that ‘arrives dynamically, it is hard and full, and its movement is large and long. With light touch it remains; with heavy pressure it has force. Its arrival and departure are both exuberant, and it can be perceived at all three levels’ (Deng 1999: p. 125). Further adding to this confusion is the existence of a number of different definitions for the same stated pulse quality, while there may be differently named pulse qualities with the same pulse definition (see TABLE 4.1 and TABLE 4.2).
TABLE 4.1 Comparison of pulse names for the Skipping, Rough and Stirred pulses
Author and source Skipping pulse (Cù mài) Rough pulse (Sè mài) Stirred pulse (Dòng mài)
Cheung & Belluomini (trans) (1982) Accelerated Difficult Agitated
Deng (1999) Skipping Rough Stirred
Flaws (1997) Skipping, rapidly, irregularly interrupted Choppy Stirring
Kaptchuk (2000) Hurried Choppy Spinning Bean
Li (Huynh, trans) (1981) Hasty Choppy Moving
Lu (1996) Running Choppy Tremulous
Maciocia (2004) Hurried Choppy Moving
O’Connor & Bensky (trans and ed) (1981) Hasty Rough Not mentioned
Porkert (1995) Agitated Grating Mobile
Morant (1994) Accelerated Hesitant Astringent Rough Turbulent
Wiseman & Ellis (1996) Skipping Interrupted Uneven Stirred
TABLE 4.2 Comparison of pulse quality definitions for the Replete pulse (Shí mài)
Author and source Definition Page no.
Deng (1999) A replete pulse …arrives dynamically, it is hard and full, and its movement is large and long. With light touch it remains; with heavy pressure it has force. Its arrival and departure are both exuberant, and it can be perceived at all three levels 125
Guanzhou Chinese Medicine College (1991) Felt at Cun, Guan and Chi forceful, long and large, on both light and heavy pressure 18
Li (Huynh, trans) (1981) Sinking, firmer than the firm pulse, and has a strong beat 15
When a pulse is felt both superficially and deeply, and has big, long, wiry, strong beats 73
Kaptchuk T (2000) Is big and also strong, pounding hard against the fingers at all three depths 199
Maciocia (2004) The Full pulse feels hard, full and rather long; it is felt easily at all levels and it has a springy quality resistant to finger pressure” Also notes the term as a description of a ‘broad range of full pulses…’ 475
Porkert (1995) Strong pulse manifesting on at least two levels. Still, the pulse shows its greatest strength and deployment on one particular level, “its specific level’ 38
Wiseman & Ellis (1996) Similar to the forceful except it is forceful on both rising and falling 120
Although the traditional pulse qualities have been named for the distinct set of features or characteristics that manifest in the pulse, the names of these specific pulse qualities are sometimes used as general descriptive terms. This arises because the changes in the pulse characteristics cluster in such a way that when a pulse quality ‘appears’ to occur as described in the literature, it may be further complicated by an additional change in another pulse characteristic, and so does not satisfactorily fit the usual description of a particular CM pulse. For example, Maciocia (2004: p. 485) describes a possible formation of a Stringlike (Wiry) (xián mài) and Slippery pulse (Huà mài) occurring with Full Liver pattern and Phlegm, which appears quite contradictory. That is, the Stringlike (Wiry) pulse is defined by the tension in the arterial wall which constrains the arterial contour from manifesting, whereas the Slippery pulse is defined by the arterial contour deforming the arterial wall, which is quite distinctly rounded as it moves under the fingers, and it is the relative lack of arterial tension which allows the pulse wave to form in this way. (There are additional changes in other pulse characteristics that further differentiate the two pulses.) So the question is, why have these two distinctly different terms been used in this way?
The answer is that they have been used in this way because the focus has been on the most apparent or distinctive change occurring in the pulse, rather than on all the information available. By focusing on the apparent changes, the increased arterial tension has been termed the Stringlike (Wiry) pulse. Yet, the classical definition of the Stringlike (Wiry) pulse notes this pulse without a distinct contour, and so by definition the pulse described by Maciocia is not the Stringlike (Wiry) pulse. Similarly, the pulse described is not the Slippery pulse either, despite the presence of Phlegm.
Yet in undertaking the process of pulse diagnosis it is hard for the practitioner not to think of the terminology of the traditional pulse qualities, if only because they have dominated any discourse of pulse diagnosis in Chinese medicine for so many years. However, it soon becomes apparent that there are limitations to the use of the pulse names when used in this way, as evidenced in the example above.
The pulse diagnosis process is further complicated when the traditional pulse names are used to discretely classify the pulse when this is not warranted (that is, when the pulse is categorised or termed as one of the traditional CM pulse qualities but not all aspects or characteristics of its presentation actually fit the traditional definition). In doing so, the other pulse characteristic changes, which do not match the traditional description of the pulse being felt, are excluded. Such an approach means all available clues about the pathogenesis are not considered in diagnoses, and so a practitioner may underestimate or overestimate the pathology against incorrectly ‘recognised’ pulse qualities rather than using all the information that is available. The obvious problem with this is that the lost pulse information may signal the difference between treatment that aims to tonify against one that aims to disperse.
4.1.1. Practical implications of confusion in CM pedagogy
The ultimate outcome of this confusion is great variance in terminology between CM texts affecting the practical application of pulse diagnosis. This includes the application of pulse diagnosis in:

• Treatment planning within clinical practice
• Educational purposes and pulse learning
• Research investigations involving traditional methods of diagnosis.
4.1.1.1. Pulse pedagogy and treatment planning
The absence of standardised pulse terminology has implications for the use of pulse diagnosis in clinical practice, where the role of pulse is thought to have various applications in diagnosis, in treatment formulation and as an immediate indicator of the effectiveness of the treatment (Birch & Felt 1999). When used for these purposes, it is vital that the pulse information is reliable, ensuring that the patient receives the correct diagnosis and so appropriate treatment. This is particularly important when using herbal medicine, as an incorrect diagnosis and hence an incorrect herbal prescription may result in a worsening of the condition. Similarly in acupuncture, there are some systems that rely on pulse assessment as the primary means of diagnosis and so treatment is dependent on a reliable and accurate assessment.
4.1.1.2. Pulse pedagogy and learning
In Asia and elsewhere Birch and Felt (1999) note that there has been a shift away from clinically based pulse teaching to a model that emphasises intellectual or theoretically based knowledge. As a result, intensive clinically based training in pulse diagnosis has fallen out of common use. The theoretical approach is commonly applied in other areas of CM education, and this pedagogical approach is usually based on the premise of a standardised and workable theoretical data set such as that used in Eight Principles differential diagnosis (Ba Gang) or Five Phases (Wu Xing). Such a standardised theoretical approach is often in contrast to the theoretical information on pulse diagnosis, with its characteristic ambiguous descriptive terms which lack clarity.
Consequently, Birch & Felt (1999: p. 235) proposed that the pulse literature was intended as a supportive adjunct to practice-based teaching, and so explains its apparent failings when used as the only form of teaching. Accordingly, they claimed, it was never meant to be the primary means of imparting knowledge in this area. Birch & Felt based their claims on historical texts that documented the traditional teaching methods of pulse diagnosis. The repetitive practice of pulse palpation under a teacher’s guidance in clinic was once the mainstay of education in this area.
The mechanisms of the pulse are fine and subtle, and the pulse images are difficult to differentiate. The bowstring and the tight, the floating and the scallion-stalk confusingly resemble one another. They may be readily distinct at heart (that is, their verbal definition may have been memorized), but it is difficult for the fingers to distinguish them. If a deep pulse is taken as a hidden one, the formula and treatment will never be in the right line. If a moderate pulse is taken as a slow one, crisis may crop up instantly. In addition, there are cases where several different kinds of pulse images appear all at the once or several different categories of disease may exhibit the same type of pulse
Other CM authors argue that pulse taking should not be difficult to learn (Porkert 1995, Flaws 1997), stressing the importance of the theories and of learning the standard textbook definition of each pulse quality (King 2001: p. 37). However, it can be strongly argued that it is precisely the lack of clarity of the standard definitions that cause problems. Wiseman and Ye (1999) note a lack of precision and non-standardised definitions arise when authors and practitioners have failed to identify exactly what they mean when stating or describing pulse characteristics (Wiseman & Ye 1999).
4.1.1.3. Pulse pedagogy and research
In research, ideally, an appropriate study method requires detailed documentation of all facets of the design process, detailing how information was collected, interpreted and decisions made using CM methods of diagnosis, leading to the development of a treatment protocol. Therefore a clear and unambiguous terminology is required here as well. In addition, the careful detailing of both treatment and diagnostic processes should be included in clinical trials (Birch 1997), not only to enable replication of the studies but also to provide clinically relevant information for the CM profession.
A failure to standardise pulse terminology and descriptions hinders the evaluation of traditional-based systems of CM, where the role of pulse is given equal weighting with other assessment approaches. For example, a holistic perspective and a method of treatment tailored to the individual are integral components of the traditional approach to CM. This involves the systematic gathering and collating of patient data to construct a diagnosis and subsequent treatment protocol. With a treatment based directly on the diagnostic assessment, it is vital that this initial process is both objective and reliable. As Flaws notes: ‘In TCM, a correct pattern discrimination is vitally important. It is the guide and foundation to successful, individualised treatment’ (Flaws 1997: p. 3).
4.2. Pulse diagnosis, subjectivity and the need for reliable assessment methods
A subjective procedure is one in which an observation or outcome arises from the individual; it is dependent on the individual’s own interpretation and therefore cannot be objectively measured or confirmed. The pulse diagnosis method, by definition, is such a procedure. Subjective procedures are prone to ambiguity, and this is clearly reflected in the pulse literature where there may be two quite contradictory descriptions for the same pulse quality. Subjective procedures are also prone to variability in their application; different practitioners may interpret the same patient’s pulse in different ways. Alternatively, the same practitioner may interpret the same patient’s pulses differently on subsequent examinations at the same sitting, as was reported by Craddock (1997).
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