Omitted Publications
Prescription
medical devices are accompanied by instructions or guidelines for their safe
and effective use. Any deviations in conducting the automated sNCT procedure
or interpreting its measures may result in erroneous and invalid diagnostic
information. None of the publications listed in the
comprehensive bibliography deviated significantly from these Manufacturers
Recommended Guidelines in their application and analysis of sNCT/CPT
studies. The publications listed below, however, were omitted from the
bibliography because the authors failed to follow the procedures established
for the proper analysis of the test data. The authors were notified about
the errors in their methodologies and Letters to the Editor were published
exposing the errors and their effect on the articles’ conclusions. However,
unlike authors of other papers who had been informed of similar problems,
the authors of these three publications never published corrections to their
papers. Note that publications below averaged both hyperesthetic
and hypoesthetic Current Perception Threshold (CPT) measures.
Additional information regarding
this type of statistical error is provided below.
1. Franzblau, A., Werner, R.A., Johnston, E., Torrey, S. Evaluation of
Current Perception Threshold Testing as a Screening Procedure for Carpal
Tunnel Syndrome among Industrial Workers. Journal of Occupational Medicine,
Volume 36(9):1015-1021, 1994. [Note: In addition to the methodological
errors in this publication, Dr. Franzblau, the principle author of this
publication, testified in a
Washington State hearing
that subsequent to this publication he changed his definition of what
constituted Carpal Tunnel Syndrome (CTS).] See letter to editor Journal of
Occupational and Environmental Medicine, Volume 37 (7) 790-793, (July 1995).
2. Vinik, A.I., Suwanwalaikorn, S., Stansberry, K.B., Holland, M.T., McNitt,
P.M., Colen, L.E. Quantitative Measurement of Cutaneous Perception in
Diabetic Neuropathy. Muscle & Nerve, Volume 18:574-584, 1995.
3. Tack, C.J.J., Netten, P.M., Sheepers, M.H., Meijer, J.W.G., Smits, P.,
Lutterman, J. Comparison of clinical examination, current and vibratory
perception threshold in diabetic neuropathy. Netherlands Journal of
Medicine, Volume 44:41-49, 1994.
4. Park R., Wallace, M.S., Schulteis, G, Relative sensitivity to alfentanil
and reliability of current perception threshold vs von Frey tactile
stimulation and thermal sensory testing. Journal of the Peripheral Nervous
System, Volume 6:232-240, 2001.
5. Shimoda, O., Ikuta, Y. The Current Perception Thresholds vary between
horizontal and 70 degree tilt-up positions. Anesthesia and Analgesia, Volume
91:398-402, 2000. See: Chado, H.N., Related letter to editor Anesthesia &
Analgesia, Volume 93:1079, 2001.
Fraudulent Publication
"AANEM Neurometer
Technology Review" American Association of Electrodiagnostic Medicine Technology Review: The
Neurometer Current Perception Threshold (CPT). Muscle & Nerve, Vol.
22,:523-531, 1999.
This AANEM publication was excluded from the bibliography because it
is fraudulent. It was falsely represented as
a peer reviewed literature review from a committee of the
American Association
of Neuromuscular and Electrodiagnostic Medicine (AANEM), nee American
Association of Electrodiagnostic Medicine (AAEM). Court documents, available upon
request, establish the article was not peer reviewed, does not represent the
consensus of a committee, was not written by 20 of the 21 authors listed,
and did not follow its own criteria for evaluating literature. Additionally
less than 19% of the cited papers in this opinion piece were actually
reviewed. The author of the publication, George Baquis, MD, stated in sworn testimony that he
had no knowledge of statistics although the review evaluation
criteria required such knowledge.
Statistical Errors in the Evaluation of CPT Measures
Averaging Measures
Averaging together CPT measures, prevents the determination of the
sensitivity of the test for conditions which may result in both
hyperesthesia and hypoesthesia.
Hyperestheia findings are similar to other biological measures, such as
serum electrolytes, which also have a "U" shaped profile as a predictive
factor for morbidity and mortality. Another example is blood pressure
measurements. Although a patient’s systolic and diastolic measures can be
averaged together, the resulting number has only minimal clinical utility.
Blood pressure measures are commonly analyzed by examining the raw systolic
and diastolic measures and comparing them to established upper and lower
ranges of healthy measures. A third example is body temperatures. If a
patient had a body temperature of 97.1°F at 10:00am, and had a body
temperature of 101.1°F at 2:00pm, then it is without question that the
patient’s temperature measures indicated an abnormality. However, if
the two temperature measures were averaged together before being evaluated,
the resultant 98.6°F average measure would falsely indicate that no
abnormality had been detected.
The CPT exam is capable of measuring the effects of conditions which can
result in abnormally high (hypoesthetic) and abnormally low (hyperesthetic)
current perception threshold levels. For example, studies have shown that
diabetic patients suffer from both hyperesthesia and hypoesthesia. Suppose
ten diabetic patients were tested with the 2000Hz stimulus on their great
toes and their CPT measures were: 1) 24, 2) 999, 3) 236, 4) 844, 5) 35, 6)
745, 7) 588, 8) 126, 9) 84, 10) 999. The established range for healthy
2000Hz CPT measures on the great toe is 179 to 523. The average of all 10
CPT measures is 468, which would be within the healthy range. In reality, of
course, nine out of the 10 patients had abnormal CPT measures. Patients 1,
5, 8 and 9 had hyperesthetic measures while patients 2, 4, 6, 7 and 10 had
hypoesthetic or anesthetic measures. Only one patient in the group (#3) had
a measure within the healthy range. For this reason it is generally not
appropriate to analyze the sensitivity of CPT data by averaging patient
measures.
Reliability
Reliability measures reproducibility, sensitivity and specificity.
Concordance, discordance, sensitivity, specificity, and variability are all
of words that have statistical definitions.
These topics
are discussed at this link.
Change Between Repeated
Measures
When evaluating the change between repeated CPT determinations, it is
generally appropriate to express the change as a percent change between
serial evaluations. Expressing the data in terms of percent change provides
a means of normalizing CPT measures between subjects. The percent change is
calculated at each testing frequency (5Hz, 250Hz and 2000Hz). This
percentage analysis also normalizes the different CPT frequency dependent
measures for the comparison.
These topics
are discussed at this link.
Coefficient of Variation
This is a valid measure of the reproducibility of repeated individual
measures and has been reported in several publications. Typically this is
expressed as the average of the percentage of the individual from their mean
CPT. Various publications have evaluated repeated CPT measurements. The
coefficient of variation for repeated measures averages approximately 6% at
2000 Hz, 12 % at 250 Hz and 16% at 5%. Each intra-subject automated
double-blind CPT determination is confirmed to a p<0.006. (Studies which
include coefficients of variation include references 1-4).
Additional
information at this link.
Prospective Evaluation
This type of study is correlated with other medical measures over time and
is more clinically oriented then the previous cited measures for example the
following publications. (See references 5-7 below).
Agreement
(Concordance) of Data Evaluation
This type of statistical evaluation is conducted to determine the rates of
agreement (concordance) and disagreement (discordance) between the CPT
studies repeated measures and the Neuval Database software evaluation of
these measures. Publications which discuss the statistical basis of the
Neuval Database software evaluation program include references 9-11 below.
Several factors can influence CPT measures including circadian rhythms age
and sex. The normative range of CPT measures is large. From a clinical point
of view, what is most significant is how consistent is the clinical
evaluation (based on the Neuval Database software evaluation) of repeated
measures. For example, if an individuals measures are “normal” today, will
they be normal tomorrow and next year? At the 1997 meeting of the American
Academy of Neurology, a group from the Mayo Clinic presented a study of the
agreement (concordance) and disagreement (discordance) of repeated EMG
(nerve conduction and electromyography (EMG) diagnoses from 200 patients
(reference 8). This study reported a discordance rate of 40% (i.e., 40% of
the time the follow-up EMG was not diagnostically consistent with the
initial EMG). Concordance or agreement of repeated CPT measurements
evaluated using the Neuval CPT evaluation is approximately 92%, while the
discordance rate of the CPT evaluation is only 8%.
References:
1) Katims, J.J., Naviasky, E., Rendell, M.S., Ng, L.K.Y., Bleecker, M.L.
Constant Current Sine Wave Transcutaneous Nerve Stimulation for the
Evaluation of Peripheral Neuropathy. Archives of Physical Medicine and
Rehabilitation, Volume 68:210-213, 1987.
2) Katims, J.J., Rouvelas, P., Sadler, B.T., Weseley, S.A. Current
Perception Threshold: Reproducibility and Comparison with Nerve Conduction
in Evaluation of Carpal Tunnel Syndrome. Transactions of the American
Society of Artificial Internal Organs, Volume 35(3):280-284, 1989.
3) Masson, E.A., Veves, A., Fernando, D., Boulton, A.J.M. Current perception
thresholds: a new, quick, and reproducible method for the assessment of
peripheral neuropathy in diabetes mellitus. Diabetologia, Volume
32:724-728, 1989.
4) Parker G., Jr., Garzione, J., Testing the Reliability for Current
Perception Threshold in the Physical Therapy Clinic. APTA Scientific Meeting
and Exposition, Physical Therapy '97, San Diego, CA, 1997.
5) Avram M.W. Neurological Complications in Chronic Uremia Management.
Morbidity and Mortality of Dialysis NIH Consensus Development Conference,
pp. 123-128, November, 1993.
6) Avram M.W. Severe Neuropathy in Urban Dialysis Patients: Neurological
Complications in Chronic Uremic Management. Contemporary Dialysis and
Nephrology, Volume 15(4):22-23,34, April, 1994.
7) Weseley, S.A., Sadler, B., Katims, J.J. Current Perception: Preferred
Test for Evaluation of Peripheral Nerve Integrity. Transactions of the
American Society of Artificial Internal Organs, Volume 34(3):188-193,
1988.
8) Smith, B.E., Stevens, J.C., Caselli, R.J., Takata, J.H., Verheijde, J.L.
and Weaver, A.L. Repeating the EMG can have a significant impact on
diagnosis of neuromuscular disease. Neurology, Volume 48 (3), Suppl.
2,P01.083, page A52, 1997).
9) Weseley, S.A., Sadler, B., Katims, J.J. Current Perception: Preferred
Test for Evaluation of Peripheral Nerve Integrity. Transactions of the
American Society of Artificial Internal Organs, Volume 34(3):188-193,
1988.
10) Katims, J.J., Rouvelas, P., Sadler, B.T., Weseley, S.A. Current
Perception Threshold: Reproducibility and Comparison with Nerve Conduction
in Evaluation of Carpal Tunnel Syndrome. Transactions of the American
Society of Artificial Internal Organs, Volume 35(3):280-284, 1989.
11) Katims, J.J., Patil, A.S., Rendell, M., Rouvelas, P., Sadler, B.,
Weseley, S.A., Bleecker, M.L. Current Perception Threshold Screening for
Carpal Tunnel Syndrome. Archives of Environmental Health, Volume
46(4):207-212, 1991.
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