Carpal tunnel syndrome in Indian patients: use of modified questionnaires for assessment

Patient selection

Seventy-six patients with hand paraesthesias (numbness, tingling, pain, and/or burning) and evidence of median nerve compression on nerve conduction study (NCS) were recruited from the hand surgery clinic of a major teaching hospital affiliated to the medical university in southern India (Rempel et al., 1998). An equal number of asymptomatic patients with matching age and gender were recruited as controls. The controls were inpatients from other surgical specialties: ear, nose and throat surgery, head and neck surgery, general surgery, vascular, gastrointestinal, hepatobiliary, pancreatic, and colorectal surgery, gynaecology, and physical medicine and rehabilitation. Patients with any pre-existing neurologic compromise of the upper extremity were excluded. The controls had to exhibit normal hand functions. Three of the controls had to be excluded due to classical/probable distributions of paraesthesias in at least two median nerve innervated digits, as defined by consensus criteria for epidemiologic study of CTS (Rempel et al., 1998).

Eleven symptomatic patients had no median nerve abnormality and were considered negative for CTS for purposes of this study (negative referrals). All study subjects completed assessment of symptom severity and functional disability by a modified version of the BCTQ. In addition the participants were evaluated for demographics, CTS risk factors, symptoms, and signs.

Symptom assessment

The initial symptoms (defined as symptoms first noticed by the patient), current symptoms (numbness, tingling, pain and burning) and their respective durations were noted in a standardised proforma (Fig 1).

Equivalent dialectical and colloquial translations of some symptoms (‘heaviness’ or ‘absence of feeling’ for numbness) were allowed. The distribution of each symptom was recorded after prompting the patient to demonstrate the affected area(s) and was later coded by an investigator according to the consensus criteria for epidemiologic definition of CTS proposed by Rempel et al. (1998), in which at least two median nerve digits affected by symptoms are a ‘classic/probable’ distribution, one median nerve innervated digit is a ‘possible’ distribution, and the remainder of distributions are ‘unlikely’. The investigator was not aware of the diagnosis while coding the hand symptom distributions.

Clinical testing

All study patients were examined by one experienced hand physiotherapist for median nerve function. The sensory threshold was assessed by SWMF testing and vibratory testing. SWMF testing was performed using five monofilaments calibrated to deliver an average force of 0.05 g (normal), 0.2 g (diminished light touch), 2 g (diminished protective sensation), 4 g (loss of protective sensation) and 300 g (loss of deep pressure sensation) (Gillis W. Long Hansen’s Disease Center, Carville, Louisiana, USA). Each monofilament (0.05–2 g) was applied to the volar aspect of the hand until the filament just bent, and the heavier monofilaments (4–300 g) were briefly touched to the skin and withdrawn. A response was considered positive if a patient could consistently detect application of the same monofilament (Weinstein, 1962). Vibratory perception threshold was assessed with 128 Hz and 256 Hz tuning forks. The patient was asked to report full vibratory sensation, partial vibratory sensation or no vibration sensation for both tuning forks after application to the interphalangeal joints in the median nerve distribution. The patient’s eyes were covered with an eye-shade during sensory threshold testing.

Tinel’s sign (Tinel, 1915) and Phalen’s test (Phalen, 1966) were assessed in the standard fashion. Motor strength of the muscles innervated by the median nerve (abductor pollicis brevis, opponens pollicis, middle and index finger lumbricals) was also assessed in the standard way.

NCS

Motor and sensory function of bilateral median and ulnar nerves were tested according to standard NCS procedures for all suspected CTS cases (Kimura, 1989). Median nerve conduction across the wrist was reported according to internal standardised values as distal latency delay, slowed conduction velocity, and/or decreased action potential amplitude. The NCS findings were classified as ‘diminished sensory response’, ‘no sensory response’, ‘diminished motor and sensory response’, ‘diminished motor and no sensory response’ and ‘absent motor and sensory response’ in order to grade severity according to the principles proposed in the development of the ‘Bland’ criteria (Bland, 2000).

Symptom severity and function disability assessment modification

The BCTQ is a questionnaire containing 11 questions regarding the severity of symptoms and concerning hand function disability. The responses are graded on a scale of 1 to 5 – no problem to severe problem (Levine et al., 1993). The BCTQ questions were first translated and then trialled during ten initial patient interview sessions conducted with the aid of Tamil, Bengali and Hindi interpreters corresponding to the patients’ native language. Review of the patients’ interview sessions was conducted with an experienced hand physiotherapist and a social worker. As mentioned before suitable modifications were made to allow for local expressions e.g. ‘buttoning of clothes’ was modified to ‘buttoning clothes or closing hooks on clothes’ and ‘holding a book while reading’ to ‘holding a book or newspaper while reading’ (Fig 2).

An interview format was used for the study assessments due to wide variations in educational background and literacy of the pilot patients. Sometimes, the order of the questions had to be changed to maintain flow. A visual analogue scale with translations of the answer choices was designed to assist patients in understanding the response choices (Fig 3).

Statistical analysis

Statistical analysis was performed using the STATA software package (Stata Corporation, College Station, Texas, USA). For every question the frequency of responses, average values and standard deviation for each questionnaire item responses were calculated for CTS cases, controls and negative referrals. Overall averages were calculated for symptom severity and function disability for subjects completing the entire questionnaire. The case group was dichotomised according to age and symptom duration. Average scores were compared by these groups and by gender with Student’s t-test. Comparison was also made between symptom severity and function disability scores for Indian patients and those reported in the Western literature (Levine et al., 1993).

The correlation between the symptom and function scores with the results of hand clinical testing and NCS severity was calculated using Pearson’s coefficient to test the validity of the modified BCTQ. The difference between average symptom and function scores in patients with and without a positive Phalen’s test and Tinel’s sign was calculated using Student’s t-test. The correlation of the items testing hand function and symptoms were tested by measuring the Cronbach’s alpha score for each subscale (i.e. symptoms and functions separately).

Usefulness in the developing world

CTS is characterised by a constellation of symptoms and physical findings, with a great variability in patient presentation (Rempel et al., 1998). Physicians in the developing world will benefit from routine use of a specific hand disability questionnaire in order to standardise their evaluation of CTS patients and capture measures of outcome undetected by traditional measurements of hand function. Therefore, questionnaires to assess symptom severity and functional disability are useful for standardising evaluation. So far, CTS have been studied primarily in Western patients and linked to risk factors of the developed world such as obesity. Since these risk factors are not frequent in the developing world, the physicians there are comparatively less experienced when evaluating and treating CTS. Further, these patients come from a variety of socioeconomic and educational backgrounds and often have difficulty describing their problems. Their complaints can often be marginalised or ignored by inexperienced physicians. The study shows that the modified BCTQ can be a useful tool to assess CTS in the Indian population and other comparable subgroups and demonstrates that the average symptoms and function score are ‘mild’ for Indian CTS patients seen in our hand clinic.

Comparison to Western patients

The symptom severity score for Indian patients was similar to that reported in Western patients; however, the function disability score was lower. Separate analysis of the severity of median nerve dysfunction demonstrated 85% of Indian patients presented with motor dysfunction on NCS, suggesting CTS in Indian patients is in fact severe on presentation. The traditional agrarian economy and reliance on manual labour in India may leave patients with no option but to continue with their daily hand functions despite peripheral nerve pain. While a direct comparison of the functional status of Western and Indian patients cannot be made, the lower functional disability score reported by Indian patients may actually indicate that the Indian patient must be tolerating more hand disablement than the Western patient. Differences in the survey scores for patients in the developing world also may be due to subtle variations in the questions during translation into the patients’ native language. Further, some functions, such as ‘gripping a telephone handle’, may not be prominent in the daily activities of the typical Indian CTS patient and thus no difficulty may be perceived. These differences highlight the importance of modifying the hand questionnaires to suit the country or community to be studied. The modifications made to the BCTQ for use in the Indian population including substituting common colloquial expressions and changing the order of the questions to make the flow of responses more intuitive contributed to the validity of the questionnaire as a survey tool in our patient population.

Validation of the Indian BCTQ

The average score for CTS cases for each symptom severity and function disability item was indeed higher than those for controls, suggesting that the survey tool measured features of hand function and symptoms affected by CTS, ascertaining the validity of the modified questionnaire. Other international groups have established the validity of translated scales when compared to other quality of life questionnaires. A Portuguese BCTQ demonstrated good correlation of symptom and function scores with grip strength and function scores with the Minnesota test (De Campos et al., 2003). In a study of 67 patients with CTS, a Turkish group was able to correlate their translated BCTQ with the Turkish ‘Short Form 36’ (SF-36, Quality Metric Incorporated, Lincoln, Rhode Island, USA), a validated psychometric evaluation of well-being (Sezgin et al., 2006). Therefore, further studies could validate the Indian BCTQ against the SF-12 (Short Form 12, which has already been translated into Indian languages), or the Disabilities of the Arm, Shoulder, and Hand questionnaire (DASH) (Hudak et al., 1996) or the Patient Evaluation Measure (PEM) (Hobby et al., 2005b; Leite et al., 2006), which have yet to be used in India.

Reliability of the Indian BCTQ

The reliability of the scale is supported by the high internal consistency of the severity items and function items. The severity and function scores of the modified BCTQ also were extremely well correlated with each other suggesting overlapping aspects of assessment. Similarly, Sezgin et al. (2006) and De Campos et al. (2003) were able to demonstrate internal consistency. Their studies went further to establish the reliability of their translated BCTQ by showing high test-retest reproducibility. In our setting, retesting subjects was limited by the time and cost considerations as most of our patients had limited resources.

Study limitations

We were unable to validate the study against provocative tests, hand strength, diminished sensation or nerve conduction studies. Therefore, another study to validate the instrument against quality of life questionnaires will be required. The interview format of the modified questionnaire eliminated unanswered survey questions, but the time required to answer the questionnaire was highly variable and occasionally very time consuming. Further work to develop a compact scoring system, particularly with the function disability items, may be useful and more practical in patients for whom CTS is already suspected prior to referral for NCS. Moreover the questionnaire will have to be phrased suitably to enable postal replies to the questionnaire thereby eliminating the need to visit a hospital, often several hundred kilometres away.

Lastly, we were unable to assess the effectiveness of our treatment using the modified BCTQ within the study time frame. This aspect may prove challenging as it would require patients to present 6 months after surgery for reassessment. Due to the socioeconomic limitations described, retention of study patients will likely be low.

The study shows that this modified BCTQ can be a useful tool to assess CTS in the Indian population and other comparable subgroups in the developing world. This study has established normative data on CTS for the Indian population.