The Accuracy of Physical Diagnostic Tests for Assessing Meniscal Lesions of the Knee: A Meta-Analysis

Differences between study characteristics are another potential source of heterogeneity of sensitivity and specificity.⁸ Those other sources of heterogeneity were assessed by adding the following characteristics to the meta-regression model: study validity items (most valid category of each item vs other categories), setting (primary care vs other), the spectrum of the diseased and the nondiseased (broad spectrum vs small spectrum), the prevalence of meniscal lesions, and the year of publication. When a significant subgroup was identified (P <.05), separate analyses were performed for each subgroup.

The summary estimates of sensitivity and specificity were used to calculate the predictive value of a positive (PV+) and negative (PV-) test result for circumstances with varying prevalences of meniscal lesions. When the sensitivities or specificities were heterogeneous between studies, however, the summary estimate of sensitivity was used for calculating predictive values with the accompanying specificity, estimated from the SROC curve.

Results

Selection of Studies

The literature search revealed a total of 402 potentially eligible studies, of which 10 were selected for inclusion.^12-21 Three other studies were found by reference tracking.^22-24 Thus, 13 studies met the selection criteria. The reply to a letter to the editor to one of the studies contained additional information and was also considered for analysis.^17,25,26

Methodologic Quality and Study Characteristics

The index test and reference standard had been measured independently (blindly) of each other in only 2 studies.^16,21 Verification bias seemed to be present in all studies (patients with an abnormal physical test result were more likely to undergo the gold standard test, inflating the sensitivity and decreasing the specificity). Nine studies applied arthroscopy as the gold standard,^{12-14,16,17,19-21,24} and 1 study used MRI.¹⁵ No study was performed in a primary care setting. In 7 studies a broad spectrum of knee lesions was reported,^{12-15,17,20,21} and in 4 studies the spectrum was not specified Table 1.^18,19,22,23 A broad spectrum of conditions in the reference group (nondiseased) was present in 8 studies,^{12-15,17,20,22,23} while in 4 studies the spectrum was not specified.^18,19,21,24 Details regarding the index tests were poorly reported, except in 2 studies.^17,21 In all studies that addressed the McMurray test, the experience of a “thud” or “click” was used for designating a test as positive.^{12,13,15-19,22} Only 2 studies mentioned assessment of the index test independent of knowledge of other clinical information (including the results of other meniscal tests).^17,21Table w2* The age and sex distribution of the patients and the duration of complaints are presented in Table 1.

Accuracy of Meniscal Tests

The accuracy of the assessment of joint effusion was determined in 4 studies, the McMurray test in 11, JLT in 10, the Apley compression test in 3, and 5 studies addressed various other tests. No data were presented in or could be derived from 1 study pertaining to joint effusion, 3 studies regarding the McMurray test,^14,23,24 and 1 study on JLT,²⁴ while from 1 study pertaining to both the McMurray test and JLT only the point estimates of the various test characteristics were reported without the original number of patients in the various categories.¹⁵ Of the study of Evans and coworkers,^17,26 who presented data of an inexperienced and experienced researcher, only the latter results were used. Of the study of Abdon and colleagues,¹⁴ who made a distinction between tenderness of the medial and posterior part of the joint line, only the data of the medial part were considered. It should be noted that 2 studies incorporated a very small number of nondiseased subjects.^23,24 Also, one of those studies presented results from individual knees instead of subjects.²⁴ Part of their results pertained to both knees of the same subject, which violates the assumption of (statistical) independence of the observations. Therefore, this study was excluded from further analysis. Finally, some studies did not make a distinction between medial and lateral meniscal lesions,^{13,17,19,22,23} while others presented the results for medial and lateral meniscal lesions separately.^{12,14,15,18,20} Of the latter studies, only the results of medial meniscal tests were used for statistical analysis.

The diagnostic accuracy of assessment of joint effusion and the various meniscal tests is shown in Table 2. There was significant heterogeneity of sensitivity and specificity of all tests, except for specificity of the Apley compression test (P=.89).

Sensitivity and specificity were negatively correlated for joint effusion (Rs = -1.0), the McMurray test (Rs = -0.43), and JLT (Rs = -0.62). This means that as one increased, the other decreased, which is to be expected. The SROC curves Figure 1 indicate little discriminative power of those meniscal tests. No significant subgroups were detected for both tests. The power of meta-regression analysis, however, was low because of the small number of available studies.