IRT scoring procedures for TIMSS data.

In large-scale international assessment programs, results for mathematics proficiency are typically reported for jurisdictions such as provinces or countries. An overall score is provided along with subscores based on content subdomains defined in the test specifications. In this paper, an alternative method for obtaining empirical subscores is described, where the empirical subscores are based on an exploratory item response theory (IRT) factor solution. This alternative scoring is intended to augment rather than to replace traditional scoring procedures. The IRT scoring method is applied to the mathematics achievement data from the Trends in International Mathematics and Science Study (TIMSS). A brief overview of the method is given, and additional material is given for validation of the empirical subscores. The ultimate goal of scoring is to provide diagnostic feedback in the form of naturally occurring item clustering. This provides useful information in addition to traditional subscores based on test specifications. As shown by Camilli and Dossey (2019), the achievement ranks of countries may change depending on which empirical subscore of mathematics is considered. Traditional subscores are highly correlated and tend to provide similar rank orders. •The methods takes advantage of the TIMSS sampling design, specifically pairs of jackknife zones, to aggregate categorical to higher-order sampling units for IRT factor analysis.•Once factor scores are estimated for sampling units and interpreted, they are aggregated to the jurisdiction level (countries, states, provinces) using sampling weights. The procedure for obtaining standard errors of jurisdictional level scores combines cross-sampling-unit variance and Monte Carlo sampling variation.•Full technical details of the IRT factoring procedures are given in Camilli and Fox (2015). Fox (2010) provides additional background for Bayesian item response modeling techniques. The estimation algorithm is based on stochastic approximation expectation-maximization (SAEM).

Limited microdiscectomy for lumbar disk herniation: a retrospective long-term outcome analysis.

OBJECTIVE AND SUMMARY OF BACKGROUND DATA: Surgical treatment of lumbar disk herniation is traditionally accomplished by removal of the extruded fragment as well as an aggressive decompression of the disk space. This retrospective study evaluates the long-term results of limited discectomy, otherwise known as fragmentectomy, for lumbar disk herniation using a minimally invasive technique. Although there are ample studies in literature regarding short-term outcome after limited microdiscectomy, there is a paucity of literature for long-term outcomes after fragmentectomy. We present long-term outcomes averaging 7 years after limited discectomy. STUDY DESIGN AND METHODS: A total of 152 patients were operated on between January 1, 2001 and June 30, 2003 for single-level herniated lumbar disks. All patients had microsurgical fragmentectomy performed through a small skin incision off the midline using a tubeless retraction system. Fifty-four patients participated in the study, whereas 98 patients were lost to long-term follow-up. Long-term outcome was assessed by telephone survey or mail-in survey using the Oswestry Low Back Pain Disability Index and a patient outcome survey. After Institutional Review Board approval and patient consent, all 54 patients had a thorough chart review for evaluation of further lumbar surgeries. The mean long-term follow-up was 86.2 months (range, 72-104 mo) or about 7.2 years. RESULTS: Forty-eight of the 54 patients (88.9%) reported an excellent (26 patients) or good (22 patients) long-term outcome with surgery. Long-term back and leg pain improvement was seen in 44 of 49 (89.8%) and 44 of 50 (88.0%) patients reporting back or leg pain, respectively. The mean Oswestry Disability Index for long-term follow-up was 8.89, indicating minimal disability. Same-level recurrences requiring reoperation were seen in 6 of the 54 patients who participated (11.1%) within the average 86.2-month follow-up. Four of 34 (11.85%) known contained herniations and 2 of 20 (10.0%) known extruded herniations presented for same-level surgical recurrence. All recurrences were successfully treated with reexploration and fragmentectomy. Two patients from the recurrence group and 1 from the original 54 progressed to need an arthrodesis at the initial operated level (5.6%). One patient in the same-level recurrence group and 2 patients from the original 54 developed an operative herniated disk at an adjacent level (5.6%). CONCLUSIONS: Our long-term outcome study shows that a minimally invasive approach to microdiscectomy with removal of the fragment only is an effective way to treat lumbar disk herniation. The rate of recurrence in our long-term study seems slightly higher compared with previously published studies, which generally had shorter follow-up periods. Long-term patient outcomes for back and leg pain were also very low. No appreciable difference in operative reherniation could be found with patients who had contained verses extruded fragments. It is difficult to predict from this study whether a simple fragmentectomy was the cause of the progression to further surgeries or whether this was the natural progression of a degenerative spine. Further prospective trials are necessary to fully understand the factors associated with limited microdiscectomy.