Jacques Pouchot

Methodological Approaches to Shortening Composite Measurement Scales

Composite measurement scales (CMSs) have contributed to improving the measurement of complex medical phenomena such as physical and psychological functioning or health-related quality of life. However, their use in patient care and research is often limited by their length and excessive respondent burden. In such situations, short instruments should be made available. Efforts to develop short instruments have largely focused on shortening existing instruments. To investigate the methodology currently used in the shortening of CMS, we assessed 42 studies reported in medical, psychological, and educational journals between 1984 and 1994. A number of methodological and statistical considerations important in the CMS shortening procedure were found to have been ignored or neglected by authors developing short forms from existing CMS. Serious flaws appear mainly to result from inadequate conceptualization of the shortening process, and inappropriate use and excess credit given to statistical techniques used to select items to be retained in short forms. When performed, the assessment of measurement properties of the short form was often inappropriate, and cross validation studies were seldom conducted. We propose recommendations for shortening existing CMS, to help authors and investigators develop and choose, respectively, shortened measurement instruments. These recommendations address the preliminary choice of the original CMS to be shortened, and the two successive phases to be considered in the development of short forms: the shortening process itself, where items are selected, and the validation of the shortened CMS, which should be conducted independently using independent subject samples.

Acquired hemophilia due to factor VIII inhibitors in 34 patients

BACKGROUND Acquired hemophilia is a rare disease caused by the development of auto-antibodies against factor VIII. SUBJECTS AND METHODS We studied the characteristics and outcomes of 34 patients (19 women and 15 men) with acquired hemophilia from 1980 to 1997. RESULTS The mean age of the patients was 61 years (range, 22-93 years). An underlying disease was observed in 18 (53%) patients: 5 patients had cancer, 4 an autoimmune disorder, 2 a dermatologic disorder, 3 asthma, 3 were postpartum, and 1 had an adverse reaction to ampicillin. Factor VIII level was <5% in 30 (90%) patients; factor VIII antibodies were elevated (>10 Bethesda units) in 23 (69%) patients. Bleeding requiring transfusions was reported in 25 (75%) patients. Human factor VIII was given to 14 patients and porcine factor VIII to 5. Six patients received prothrombin complex concentrates and one desmopressin. Several immunosuppressive treatments were used, mainly corticosteroids, cyclophosphamide, and intravenous immunoglobulin. Bleeding stopped in all but one patient within 2 weeks. Most patients achieved complete remission, although two relapses were observed subsequently. CONCLUSION This large study helps to clarify the presentation and clinical course of acquired hemophilia. Prospective studies are needed to determine the efficacy of treatment.

Reliability of Tuberculin Skin Test Measurement

The tuberculin skin test has many potential sources of error and variability. Standardization of the tuberculin reagent and the meaning of the test results have been considered in some detail [1, 2], but little attention has been paid to the reading itself [3-10]. Measurement of the induration, however, is one of the most important potential sources of error. If the customary technique of palpation is used, the margins of the induration may be difficult to define. The alternative ballpoint-pen method, although advocated as more reliable than palpation [3], has not been discussed in official statements on tuberculosis [1, 2]. We investigated the reliability of the ballpoint-pen technique and compared this technique with the palpation method. Methods Patients and Procedures Patients and health care personnel who were in an internal medicine department and needed a tuberculin skin test were invited to participate. Persons who had received bacille CalmetteGurin vaccine were enrolled preferentially. Ninety-six persons who provided informed consent ultimately participated in the study. Tuberculin Skin Tests and Measurement Methods Ten units of tuberculin from Pasteur Merieux, Lyon, France (corresponding to the recommended 5 IU of purified protein derivative tuberculin), were injected intradermally on the volar surface of the forearm (Mantoux technique) [11]. Readings were done on the third day after the test was administered, and the diameter of induration was measured along the long axis of the forearm. Two experienced investigators each independently did three measurements. The first two measurements were taken with a blinded caliper using the ballpoint-pen technique [3]. With this technique, a medium-point ballpoint pen is used to draw a line starting 1 to 2 cm away from the skin reaction and moving toward its center. When the pen reaches the margin of the induration, an increased resistance to further movement is felt and the pen is lifted. The procedure is repeated on the opposite side of the skin reaction. The distance between the ends of the opposing lines at the margins of the induration is measured. In our study, the lines were erased and the measurement process was repeated. The lines were then erased again, and the third measurement was done by palpation [2]. To reproduce the usual conditions of testing, we used a flexible ruler. The data were collected during eight sessions; 11 to 14 participants were tested per session. To reduce the chance that an observer would remember previous readings, three things were done. First, the results of measures that were obtained with the blinded caliper were recorded by a third investigator. Second, the first ballpoint-pen measure was done for all participants at each session, then the second ballpoint-pen measure, and then the palpation measure. Third, before the second and third readings, the third investigator verified that no minor landmarks persisted. Statistical Analysis To analyze the reliability of quantitative data, we used statistical methods that have been described elsewhere [12]. Intraclass correlation coefficients and their 95% CIs were computed using SAS soft-ware (SAS Institute, Cary, North Carolina) [13]. Induration diameters were used to classify skin reactions as positive or negative according to the 5-, 10-, and 15-mm cutoff points that have been recommended as indicating positivity in various situations [2]. Reliability was then assessed with coefficients [14]. We also used a graphical analysis that focuses on the mean and the variation in the differences between repeated measurements [15]. Mean differences and the SD of the differences were calculated. An area of imprecision that was determined on the basis of the SD of the differences was placed around the arbitrarily chosen 10-mm cutoff value (10 mm 1.96 SD). If a first measurement fell within this area, particularly at or about the cutoff value, the likelihood that the second measurement would be sufficiently different to change the result of the tuberculin skin test from negative to positive (or vice versa) was high. Conversely, such reclassification would occur in only 5% of the cases that had values outside this area. Results Because of the study design, only 27 participants (28%) did not react to the tuberculin skin test. Reliability of the Ballpoint-Pen Technique Intraobserver Reliability In persons who had no response to the tuberculin skin test, the intraobserver reliability was perfect (intraclass correlation coefficient = 1.0). Intraclass correlation coefficients were high for both observers and decreased only slightly after the nonresponders were excluded. The coefficients also suggested good intraobserver reliability but were lower with the 10- and 15-mm cutoff values than with the 5-mm cutoff value (Table 1). Table 1. Reliability Study of the Ballpoint-Pen and Palpation Methods of Induration Measurement for the Tuberculin Skin Test The top panel of Figure 1 shows the difference between the two readings for each participant that were done by the first observer (range, 6.8 to +3.5 mm) plotted against the corresponding mean for each participant. The level of intraobserver reliability was evaluated by determining the 95% CI ( 2.68 to +2.96 mm) within which most of the differences were seen. This means that 5% of the time, the second measure of the test results done by using the ballpoint-pen method would be at least 2.7 mm less than or 3.0 mm more than the first one. This lack of reliability could lead to the reclassification of a negative tuberculin skin test result as positive or vice versa. Figure 1. Top. Middle. Bottom. As shown in the top panel of Figure 1, an area of imprecision that straddles the cutoff value (7.2 to 12.8 mm for a 10-mm cutoff value) was generated using the SD of the differences. Test results for 8 of the 69 patients (12%) were reclassified. The first measurement for 30 of the 69 patients (43.5%) fell within this area of imprecision; 7 of those 30 patients (23.3%) were among the 8 patients whose test results were reclassified. Interobserver Reliability Agreement between observers, estimated by using the intraclass correlation and coefficients, was high (Table 1). The first ballpoint-pen measures made by the two observers were used for these analyses. Differences between first measures done by the two observers were between 5.1 and +7.3 mm (Figure 1, middle). The 95% CI of the differences was 3.39 to +3.69 mm; this means that 5% of the time, the result of a second tuberculin skin test measurement by another investigator would be at least 3.4 mm more than or 3.7 mm less than that of a first investigator. As in the top panel of Figure 1, an area of imprecision (6.5 to 13.5 mm) is shown in the middle panel of Figure 1; this area is slightly broader than that calculated for intraobserver reliability. Test results for 8 of the 69 patients (12%) were reclassified. The first measurement for 40 of the 69 patients (58%) fell within this area of imprecision; 7 of those 40 patients (17.5%) were among the 8 patients whose results were reclassified. Reliability of the Palpation Technique Except for the coefficients at the 15-mm cutoff, assessment of agreement between observers showed that all reliability coefficients obtained with the palpation technique were slightly lower than those obtained with the ballpoint-pen method (Table 1). The 95% CI of the differences between the measures of the two observers was 4.6 to +5.2 mm (Figure 1, bottom). This resulted in a much broader area of imprecision for the readings (5.1 to 14.9 mm). Test results were reclassified for 12 of the 69 patients (17.4%). The first measure of 43 of the 69 patients (62.3%) fell within this area of imprecision, and the 12 patients whose test results were reclassified were among those 43 (27.9%). Agreement between Ballpoint-Pen and Palpation Methods Although all the intraclass correlation coefficients were high, the coefficients that were produced after persons with no response to the test were excluded suggested only moderate to good reliability (Table 1). The 95% CIs of the differences between the first ballpoint-pen and the palpation measures were 3.0 to +4.1 mm for readings taken by the first observer and 2.5 to +3.9 mm for readings taken by the second observer. The areas of imprecision for the measurements were from 6.4 to 13.6 mm for readings taken by the first observer and 6.8 to 13.2 mm for readings taken by the second observer. Reclassification occurred in 8 of 69 patients (12%) for both observers. Discussion In our study, the ballpoint-pen technique was reliable, as evaluated by global reliability coefficients. However, the graphical analysis provided a more meaningful representation of the level of variation. Intraobserver reliability may be the most important factor for such diagnostic tests as the tuberculin skin test, which are usually done by only one examiner for any given patient. Lack of reliability may lead to the frequent reclassification of results, particularly if readings are at or about the cutoff values. Reliability coefficients were slightly higher for the ballpoint-pen technique than for the palpation method. In addition, the 95% CI of the differences of the measures taken by the two observers was 38% broader for the palpation method than for the ballpoint-pen technique; this could result in more frequent misclassification. Only one study [10] has addressed the interobserver reliability of the ballpoint-pen technique. That study relied on simple correlation coefficients to determine reliability. Reanalysis of the data from that study provided a coefficient of 0.74 (using a cutoff point of 10 mm). Previous studies of the reliability of the palpation method [5, 6, 10] have also been restricted primarily to the assessment of interobserver agreement and have provided conflicting results. Recalculation from the data of one large survey of six studies on tuberculin skin testing [4] gave

Methodological issues in determining the dimensionality of composite health measures using principal component analysis: case illustration and suggestions for practice.

During the early steps of the construction of composite health measures, principal component analysis (PCA) is commonly used to identify ‘latent’ factors that underlie observed variables and to determine the dimensionality of the instruments. The determination of the number of components to retain is critical to PCA: it markedly influences the factorial model identified and further conditions the validity of the constructed instrument. However, many researchers developing composite health measures seem to be unaware of the importance of this determination. The purposes of the paper are to illustrate (1) the variability of the factorial models obtained by using different published rules (n=10) for determining the number of components to retain in PCA applied to two quality-of-life datasets, and (2) the value of a careful and diversified approach to the problem of the number of components to retain in PCA that we suggest, instead of the unsatisfactory ‘rule-of-thumb’ that many researchers use. This involves: (1) using robust rules (including parallel analysis and minimum average partial procedure) to generate a set of possible values for the number of components to retain, (2) repeating the analysis across samples, (3) comprehensively assessing the models obtained, and (4) considering complementary methods to PCA and especially confirmatory factor analysis.

Diagnosis and treatment of ossification of the posterior longitudinal ligament of the spine : report of eight cases and literature review

PURPOSE Ossification of the posterior longitudinal ligament (OPLL) is a common, well-recognized cause of spinal stenosis and myelopathy in Japan. Although also common in whites, especially among the elderly, it has received little scientific attention. We wish to increase awareness of this important cause of myelopathy, and to determine if the clinical characteristics of OPLL are similar in non-Japanese and Japanese patients. PATIENTS AND METHODS The clinical and radiologic features of eight cases of OPLL are presented. These cases combined with 73 non-Japanese cases gathered from the English literature are contrasted with 2,125 Japanese cases of OPLL. RESULTS Similarities among non-Japanese and Japanese cases included: (1) male predominance; (2) peak age at onset of symptoms in the sixth decade; (3) clinical presentation, which ranged from asymptomatic to quadriplegia, with progressive or acute onset of neurologic deterioration; (4) greater than 95% localization to the cervical spine, spastic quadriparesis being the most common neurologic presentation; (5) an association with several rheumatic conditions including diffuse idiopathic skeletal hyperostosis (DISH), spondylosis, and ankylosing spondylitis; and (6) neurologic improvement with either conservative or surgical treatment in a significant proportion of patients. Differences between the two groups were minimal and included a higher mean age at onset (although onset in both groups occurred within the sixth decade) and a greater proportion of patients with DISH and with the continuous type of OPLL in the non-Japanese group. CONCLUSION The clinical characteristics of OPLL are similar in Japanese and non-Japanese patient populations. Increased awareness of this condition, which has potentially devastating neurologic complications, will favorably influence diagnosis, treatment, and outcome.

Helicobacter cinaedi Septic Arthritis and Bacteremia in an Immunocompetent Patient

We report on the first case of documented Helicobacter cinaedi septic arthritis in an immunocompetent heterosexual young man. The patient presented no identified risk factor except for contact with animals that have been incriminated as a possible source of infection, particularly for these patients. Despite prolonged bacteremia, the response to long-term therapy with ciprofloxacin and rifampin was excellent.

Tuberculosis, of the sacroiliac joint: clinical features, outcome, and evaluation of closed needle biopsy in 11 consecutive cases

Sacroiliac joint (SIJ) involvement has been reported in up to 9.7 percent of patients with skeletal tuberculosis. Lack of awareness of this now uncommon form of infection often leads to diagnostic delay and increased morbidity. Eleven consecutive cases of SIJ tuberculosis are reported; clinical and radiologic features, diagnosis, treatment, and outcome are discussed. Buttock pain was the presenting complaint in all patients. However, radicular pain in the lower back (seven patients) or lower limb (10 patients) was common and in one patient precipitated an unnecessary surgical intervention. SIJ tuberculosis is frequently an isolated phenomenon. Therefore, direct sampling of the SIJ is necessary to establish the diagnosis. The recently described technique of closed needle biopsy of the SIJ was employed in all 11 patients and established the diagnosis in nine of the 11.

A preliminary score for the assessment of disease activity in hereditary recurrent fevers: results from the AIDAI (Auto-Inflammatory Diseases Activity Index) Consensus Conference

Background The systemic autoinflammatory disorders (SAID) share many clinical manifestations, albeit with variable patterns, intensity and frequency. A common definition of disease activity would be rational and useful in the management of these lifelong diseases. Moreover, standardised disease activity scores are required for the assessment of new therapies in constant development. The aim of this study was to develop preliminary activity scores for familial Mediterranean fever, mevalonate kinase deficiency, tumour necrosis factor receptor-1-associated periodic syndrome and cryopyrin-associated periodic syndromes (CAPS). Methods The study was conducted using two well-recognised consensus formation methods: the Delphi technique and the nominal group technique. The results from a two-step survey and data from parent/patient interviews were used as preliminary data to develop the agenda for a consensus conference to build a provisional scoring system. Results 24 of 65 experts in SAID from 20 countries answered the web questionnaire and 16 attended the consensus conference. There was consensus agreement to develop separate activity scores for each disease but with a common format based on patient diaries. Fever and disease-specific clinical variables were scored according to their severity. A final score was generated by summing the score of all the variables divided by the number of days over which the diary was completed. Scores varied from 0 to 16 (0–13 in CAPS). These scores were developed for the purpose of clinical studies but could be used in clinical practice. Conclusion Using widely recognised consensus formation techniques, preliminary scores were obtained to measure disease activity in four main SAID. Further prospective validation study of this instrument will follow.

Validation of the French version of the Childhood Health Assessment Questionnaire (CHAQ) in juvenile idiopathic arthritis

OBJECTIVES To translate, cross-culturally adapt, and validate the functional disability tool Childhood Health Assessment Questionnaire (CHAQ), a variant of the Health Assessment Questionnaire (HAQ), in children with juvenile idiopathic arthritis (JIA). CHILDREN AND METHODS The disability index is the mean of the scores on the eight domains of the CHAQ and can range from 0 (no disability) to 3 (maximum disability). The CHAQ was first translated into French and adapted, then validated in a multicenter cross-sectional study in 306 children with JIA (systemic onset, 23%; polyarticular onset, 22%; extended oligoarticular subtype, 25%; and persistent oligoarticular subtype, 30%). RESULTS Overall CHAQ scores discriminated between the four JIA subtypes (systemic: 1.1 +/- 0.9; polyarticular: 0.8 +/- 0.7, extended oligoarticular 0.8 +/- 0.7, and persistent oligoarticular: 0.4 +/- 0.5 [P < 0.0001]). Reproducibility evaluated by test-retest at a 7-day interval was excellent (intraclass coefficient, 0.91), as was agreement between the Parents and Childrens versions of the questionnaire (intraclass coefficient, 0.89). Significant correlations were found between the overall CHAO score and variables reflecting disease severity (joint counts, physicians and parents global assessments, and erythrocyte sedimentation rate), indicating excellent convergent validity of the tool. CONCLUSION The French version of the CHAQ displays good psychometric characteristics, although its sensitivity to change remains to be established. The French version of the CHAO should prove useful in international studies and can be expected to be helpful for monitoring individual patients with JIA.

Manifestations cliniques et biologiques de la maladie de Still de l’adulte

Resume Une triade La maladie de Still de l’adulte (MSA) est une affection rare qui associe classiquement une fievre elevee hectique, une eruption cutanee evanescente constituee de petites macules roses saumonees, et des arthrites. Des manifestations systemiques nombreuses Une douleur pharyngee est frequente et contribue souvent a egarer le diagnostic. Un peu plus de 60 % des patients ont des adenopathies mobiles indolores, le plus souvent cervicales. L’atteinte hepatique est frequente et ne se traduit le plus souvent que par une cytolyse moderee. Toutefois, la possibilite d’hepatites cytolytiques gravissimes justifie une surveillance rigoureuse de la biologie hepatique. Parmi les nombreuses autres manifestations systemiques decrites, il faut retenir l’atteinte pericardique parfois responsable d’une tamponnade, l’atteinte du parenchyme pulmonaire parfois responsable d’un syndrome de detresse respiratoire aigue, les rares atteintes neurologiques le plus souvent sous la forme d’une meningite aseptique ou d’une paralysie d’un nerf crânien. Au point de vue biologique Le syndrome inflammatoire est constant et tres marque, et il existe classiquement une franche hyperleucocytose a polynucleaires neutrophiles. L’enquete infectieuse est negative et les examens immunologiques generalement non contributifs. L’elevation de l’IL-18 pourrait avoir un interet diagnostique et pronostique. C’est surtout la presence d’une hyperferritinemie, bien plus elevee que ne le voudrait le seul syndrome inflammatoire, qui a une valeur diagnostique, surtout lorsqu’elle s’associe a une diminution de sa fraction glycosylee, en deca de 20 %.