393
6. Laing FC, Jeffrey RB, Wing VW. Improved visualisation of choledocholithiasis by sonography. AJR 1984; 143: 949-52. 7. Baron RL. Common bile duct stones: reassessment of criteria for CT diagnosis. Radiology 1987; 162: 419-24. 8. Darweesh RMA, Dodds WJ, Hogan WJ, et al. Fatty meal sonography for evaluating patients with suspected partial common duct obstruction. AJR 1988; 151: 63-68. 9. Campbell JP, Wilson SR. Pancreatic neoplasms: how useful is evaluation with US? Radiology 1988; 167: 341-44. 10. Iishi H, Yamamura H, Tatsuta M, et al. Value of ultrasonographic examination combined with measurement of serum tumour markers in the diagnosis of pancreatic cancer of less than 3 cm in diameter. Cancer 1986; 57: 1947-51. 11. Freeny PC, Marks WM, Ryan JA, Traverso LW. Pancreatic ductal adenocarcinoma: dynamic bolus CT diagnosis and staging and results of treatment. Radiology 1988; 166: 125-33.
Jones SN, Lees WR, Frost RA. Diagnosis and grading of chronic pancreatitis by morphological criteria derived by ultrasound and pancreatography. Clin Radiol 1988; 39: 43-48. 13. Reiman TH, Balfe DM, Weyman PJ. Suprapancreatic biliary obstruction: CT evaluation. Radiology 1987; 163: 49-56. 14. Nesbit GM, Johnson CD, James EM, MacCarty RL, Nagorney DM, Bender CE. Cholangiocarcinoma: diagnosis and evaluation of resectability by CT and sonography as procedures complementary to cholangiography. AJR 1988; 151: 933-38. 15. Dooms GC, Kerlan RK, Hricak H, Wall SD, Margulis AR. Cholangiocarcinoma: imaging by MR. Radiology 1986; 159: 89-94. 16. Scharschmidt BF, Goldberg GI, Schmid R. Approach to the patient with cholestatic jaundice. N Engl J Med 1983; 308: 1515-19. 17. Amouyal P, Palazzo L, Amouyal G, et al. Endosonography: promising method for diagnosis of extrahepatic cholestasis. Lancet 1989; ii: 12.
1195-98.
Efficacy of provocative tests for diagnosis of carpal tunnel syndrome
The validity of twelve provocative tests for carpal tunnel syndrome (CTS) in a random sample of 504 people from the general population was assessed. 50 woke up at night due to paraesthesiae (with or without numbness or pain) in the fingers innervated by the median nerve (CTS symptoms) in 93 hands. CTS was neurophysiologically confirmed in 28 subjects (44 hands)—a prior probability for CTS of 47%. All clinical diagnostic tests had a low validity. Posterior probability of CTS ranged from 35 to 70% for positive test results and from 41 to 62% for negative test results. A combination of three tests with relatively high validity (paresis of abductor pollicis brevis muscle, hyperpathia, and flick sign) did not significantly change the probability of CTS. Patients with CTS symptoms should be referred directly for neurophysiological examination. Lancet 1990; 335: 393-95.
Introduction Numerous tests have been advocated for diagnosis of carpal tunnel syndrome (CTS).1-m Patients with this disorder complain of paraesthesiae (with or without numbness or pain) involving fingers innervated by the median nerve (CTS symptoms); these symptoms are most prominent at night and often wake the patient. We have shown (unpublished) that nearly half of such patients have a neurophysiologically confirmed CTS. We here question the validity of current CTS-related
provocative tests.
Subjects and
methods
Subjects Between September, 1983, and July, 1985, adults were randomly chosen from the general population of Maastricht and surrounding
villages. Of 715 selected subjects, 504 (164 men, 340 women) were willing to be interviewed, of whom 4 had recently had surgery for CTS. The remaining 500 were asked: "Do you wake up at night because of tingling (with or without pain or numbness) in your fmgers?". 69 people said "yes" and were invited for further testing, of whom 14 subsequently withdrew. The other 55 subjects were interviewed for the second time: 5 said that their complaints had disappeared. Thus, 50 subjects were available for study. Clinical diagnostic tests were examined by M. dK; testing was done without of the neurophysiological examination results. Tests knowledge were scored positive or negative for CTS only for the hand about which the patient complained. The following tests were done:
All patients
Flick sign. The patient was asked if flicking movements with wrist and fingers eliminated the symptoms in the hand.10 Thenar
The hand
inspected for thenar atrophy. Paresis abductor pollicis brevis. The strength of this muscle was estimated manually. Paresis opponens pollicis. The strength of this muscle was estimated manually. Wrist extension test. The patient was asked to keep both hands with the wrist in complete dorsal extension for 1 min. If numbness or tingling were produced or exaggerated in the median nerve distribution of the hand within 60 s, the test was judged to be positive.6 Phalen’s test. The patient was asked to keep both hands with the wrist in complete palmar flexion for 1 min. The test was scored as wasting.
was
for the wrist extension test.8
ADDRESSES: Departments of Neurology (M. C. T. F. M. de Krom, MD), Epidemiology and Health Care Research (Prof P. G. Knipschild, MD), and Clinical Neurophysiology (Prof F. Spaans, MD), University Hospital Maastricht; and Department of Medical Informatics and Statistics (A D. M. Kester, PhD), University of Limburg, Maastricht, the Netherlands. Correspondence to Dr M. C. T. F.M. de Krom, Department of Neurology, University Hospital Maastricht, PO Box 1918, 6201 BX Maastricht, the Netherlands.
394
TABLE I-PROVOCATIVE TESTS FOR CTS
segment; the antidromic ulnar nerve sensory conduction was measured from the wrist to ring and little fingers.1s Distances between the median and ulnar stimulation sites at the wrist and the recording electrodes on the ring finger were equal. The difference in distal sensory latency (A DSL) to the ring finger between median and ulnar nerve fibres was regarded as normal if it did not exceed 0-4 ms. The upper limit for the median nerve DML was 4-5 ms.1s Skin temperature at the wrist was at least 32°C in all
patients. With methods described above, 5% or less of the CTS cases are missed.16-20 We took as our gold standard for CTS a combination of the typical CTS symptoms (with a frequency of twice a week or more) and abnormal nerve conduction of the median nerve at the wrist. Recorded signs of polyneuropathy should be absent.
Statistical analysis The relation of the diagnostic tests with the gold standard was assessed by means of X2 tests, separately for left and right hands to avoid effects of dependence between hands. As an overall performance index for each test, we calculated iota for the diagnostic Results are shown as Prior probability 47%
(no of hands positive/no of hands negative).
T+ /T- = posterior probability of a positive/negative test.
*p < 0 05 (x2-test). tThls test
was
not
done in 1
woman
Pnor
probability was 48%
Tourniquet test A pneumatic blood pressure cuff, placed above the elbow, was inflated to above the patient’s systolic pressure. The test was scored as for the wrist extension test.3 Tinel’s sign was elicited by finger percussion of the median nerve the flexor retinaculum. The test was regarded as positive if there was tingling in the area innervated by the median nerve.2,12-14
validity-ie, (observed validity - chance validity) = ( 1- chance validity)." The nearer iota is to 1, the more valid is the test. If iota is close to zero or negative the test is invalid. Calculations were done with the combined data of both hands. The value of each test in clinical practice was represented by the estimated posterior probability of a positive (or negative) test result, which is the proportion of neurophysiologically confirmed CTS-hands among the hands with a positive (negative) test. Posterior probabilities were then compared with the prior probability (the proportion of neurophysiologically confirmed CTS-hands among all tested
hands).
at
Pressure test. If pressure on the place where the median nerve leaves the carpal tunnel caused pain, the test was scored positive.7
/.
6. Laing FC, Jeffrey RB, Wing VW. Improved visualisation of choledocholithiasis by sonography. AJR 1984; 143: 949-52. 7. Baron RL. Common bile duct stones: reassessment of criteria for CT diagnosis. Radiology 1987; 162: 419-24. 8. Darweesh RMA, Dodds WJ, Hogan WJ, et al. Fatty meal sonography for evaluating patients with suspected partial common duct obstruction. AJR 1988; 151: 63-68. 9. Campbell JP, Wilson SR. Pancreatic neoplasms: how useful is evaluation with US? Radiology 1988; 167: 341-44. 10. Iishi H, Yamamura H, Tatsuta M, et al. Value of ultrasonographic examination combined with measurement of serum tumour markers in the diagnosis of pancreatic cancer of less than 3 cm in diameter. Cancer 1986; 57: 1947-51. 11. Freeny PC, Marks WM, Ryan JA, Traverso LW. Pancreatic ductal adenocarcinoma: dynamic bolus CT diagnosis and staging and results of treatment. Radiology 1988; 166: 125-33.
Jones SN, Lees WR, Frost RA. Diagnosis and grading of chronic pancreatitis by morphological criteria derived by ultrasound and pancreatography. Clin Radiol 1988; 39: 43-48. 13. Reiman TH, Balfe DM, Weyman PJ. Suprapancreatic biliary obstruction: CT evaluation. Radiology 1987; 163: 49-56. 14. Nesbit GM, Johnson CD, James EM, MacCarty RL, Nagorney DM, Bender CE. Cholangiocarcinoma: diagnosis and evaluation of resectability by CT and sonography as procedures complementary to cholangiography. AJR 1988; 151: 933-38. 15. Dooms GC, Kerlan RK, Hricak H, Wall SD, Margulis AR. Cholangiocarcinoma: imaging by MR. Radiology 1986; 159: 89-94. 16. Scharschmidt BF, Goldberg GI, Schmid R. Approach to the patient with cholestatic jaundice. N Engl J Med 1983; 308: 1515-19. 17. Amouyal P, Palazzo L, Amouyal G, et al. Endosonography: promising method for diagnosis of extrahepatic cholestasis. Lancet 1989; ii: 12.
1195-98.
Efficacy of provocative tests for diagnosis of carpal tunnel syndrome
The validity of twelve provocative tests for carpal tunnel syndrome (CTS) in a random sample of 504 people from the general population was assessed. 50 woke up at night due to paraesthesiae (with or without numbness or pain) in the fingers innervated by the median nerve (CTS symptoms) in 93 hands. CTS was neurophysiologically confirmed in 28 subjects (44 hands)—a prior probability for CTS of 47%. All clinical diagnostic tests had a low validity. Posterior probability of CTS ranged from 35 to 70% for positive test results and from 41 to 62% for negative test results. A combination of three tests with relatively high validity (paresis of abductor pollicis brevis muscle, hyperpathia, and flick sign) did not significantly change the probability of CTS. Patients with CTS symptoms should be referred directly for neurophysiological examination. Lancet 1990; 335: 393-95.
Introduction Numerous tests have been advocated for diagnosis of carpal tunnel syndrome (CTS).1-m Patients with this disorder complain of paraesthesiae (with or without numbness or pain) involving fingers innervated by the median nerve (CTS symptoms); these symptoms are most prominent at night and often wake the patient. We have shown (unpublished) that nearly half of such patients have a neurophysiologically confirmed CTS. We here question the validity of current CTS-related
provocative tests.
Subjects and
methods
Subjects Between September, 1983, and July, 1985, adults were randomly chosen from the general population of Maastricht and surrounding
villages. Of 715 selected subjects, 504 (164 men, 340 women) were willing to be interviewed, of whom 4 had recently had surgery for CTS. The remaining 500 were asked: "Do you wake up at night because of tingling (with or without pain or numbness) in your fmgers?". 69 people said "yes" and were invited for further testing, of whom 14 subsequently withdrew. The other 55 subjects were interviewed for the second time: 5 said that their complaints had disappeared. Thus, 50 subjects were available for study. Clinical diagnostic tests were examined by M. dK; testing was done without of the neurophysiological examination results. Tests knowledge were scored positive or negative for CTS only for the hand about which the patient complained. The following tests were done:
All patients
Flick sign. The patient was asked if flicking movements with wrist and fingers eliminated the symptoms in the hand.10 Thenar
The hand
inspected for thenar atrophy. Paresis abductor pollicis brevis. The strength of this muscle was estimated manually. Paresis opponens pollicis. The strength of this muscle was estimated manually. Wrist extension test. The patient was asked to keep both hands with the wrist in complete dorsal extension for 1 min. If numbness or tingling were produced or exaggerated in the median nerve distribution of the hand within 60 s, the test was judged to be positive.6 Phalen’s test. The patient was asked to keep both hands with the wrist in complete palmar flexion for 1 min. The test was scored as wasting.
was
for the wrist extension test.8
ADDRESSES: Departments of Neurology (M. C. T. F. M. de Krom, MD), Epidemiology and Health Care Research (Prof P. G. Knipschild, MD), and Clinical Neurophysiology (Prof F. Spaans, MD), University Hospital Maastricht; and Department of Medical Informatics and Statistics (A D. M. Kester, PhD), University of Limburg, Maastricht, the Netherlands. Correspondence to Dr M. C. T. F.M. de Krom, Department of Neurology, University Hospital Maastricht, PO Box 1918, 6201 BX Maastricht, the Netherlands.
394
TABLE I-PROVOCATIVE TESTS FOR CTS
segment; the antidromic ulnar nerve sensory conduction was measured from the wrist to ring and little fingers.1s Distances between the median and ulnar stimulation sites at the wrist and the recording electrodes on the ring finger were equal. The difference in distal sensory latency (A DSL) to the ring finger between median and ulnar nerve fibres was regarded as normal if it did not exceed 0-4 ms. The upper limit for the median nerve DML was 4-5 ms.1s Skin temperature at the wrist was at least 32°C in all
patients. With methods described above, 5% or less of the CTS cases are missed.16-20 We took as our gold standard for CTS a combination of the typical CTS symptoms (with a frequency of twice a week or more) and abnormal nerve conduction of the median nerve at the wrist. Recorded signs of polyneuropathy should be absent.
Statistical analysis The relation of the diagnostic tests with the gold standard was assessed by means of X2 tests, separately for left and right hands to avoid effects of dependence between hands. As an overall performance index for each test, we calculated iota for the diagnostic Results are shown as Prior probability 47%
(no of hands positive/no of hands negative).
T+ /T- = posterior probability of a positive/negative test.
*p < 0 05 (x2-test). tThls test
was
not
done in 1
woman
Pnor
probability was 48%
Tourniquet test A pneumatic blood pressure cuff, placed above the elbow, was inflated to above the patient’s systolic pressure. The test was scored as for the wrist extension test.3 Tinel’s sign was elicited by finger percussion of the median nerve the flexor retinaculum. The test was regarded as positive if there was tingling in the area innervated by the median nerve.2,12-14
validity-ie, (observed validity - chance validity) = ( 1- chance validity)." The nearer iota is to 1, the more valid is the test. If iota is close to zero or negative the test is invalid. Calculations were done with the combined data of both hands. The value of each test in clinical practice was represented by the estimated posterior probability of a positive (or negative) test result, which is the proportion of neurophysiologically confirmed CTS-hands among the hands with a positive (negative) test. Posterior probabilities were then compared with the prior probability (the proportion of neurophysiologically confirmed CTS-hands among all tested
hands).
at
Pressure test. If pressure on the place where the median nerve leaves the carpal tunnel caused pain, the test was scored positive.7
/.
