Construct validity and factor structure of the K-10 among Ugandan adults

BACKGROUND

Psychological distress is often used as a proxy measure for the mental health of a population. The Kessler Psychological Distress Scale (K-10) is a widely used brief screening tool for psychological distress, yet few studies have evaluated its utility in sub-Saharan Africa. We evaluated its construct validity and factor structure in Uganda.

METHODS

We used data from an ongoing case-control study. Participants in the present study were patients seeking general medical outpatient services and caretakers of mentally ill persons. Demographic data were collected using a structured questionnaire, and psychological distress was assessed using the K-10. K-10 construct validity and factorial structure were assessed through exploratory factor analysis (EFA) and confirmatory factor analysis (CFA).

RESULTS

A total of 2104 participants were included in this analysis, these were controls from a general medical setting. The mean K-10 score was 2.34 with an internal consistency of 0.86. EFA resulted in a two-factor solution that accounted for 78.37% of the variance. CFA revealed that a unidimensional model of psychological distress with correlated errors between some of K-10 items was superior, with a comparative fit index of 0.95, Tucker-Lewis index of 0.93, and a root mean square error of approximation of 0.08.

LIMITATIONS

The study was limited to evaluating internal consistency and construct validity. Future studies are warranted to examine criterion validity and establish cut-offs for psychological distress.

CONCLUSIONS

The K-10 had good psychometric properties in this population and may be useful for measuring broad psychological distress in general medical settings.

The natural history of pain and neuropathic pain after knee replacement: a prospective cohort study of the point prevalence of pain and neuropathic pain to a minimum three-year follow-up

A small proportion of patients have persistent pain after total knee replacement (TKR). The primary aim of this study was to record the prevalence of pain after TKR at specific intervals post-operatively and to ascertain the impact of neuropathic pain. The secondary aim was to establish any predictive factors that could be used to identify patients who were likely to have high levels of pain or neuropathic pain after TKR. A total of 96 patients were included in the study. Their mean age was 71 years (48 to 89); 54 (56%) were female. The mean follow-up was 46 months (39 to 51). Pre-operative demographic details were recorded including a Visual Analogue Score (VAS) for pain, the Hospital Anxiety and Depression score as well as the painDETECT score for neuropathic pain. Functional outcome was assessed using the Oxford Knee score. The mean pre-operative VAS was 5.8 (1 to 10); and it improved significantly at all time periods post-operatively (p < 0.001): (from 4.5 at day three to five (1 to 10), 3.2 at six weeks (0 to 9), 2.4 at three months (0 to 7), 2.0 at six months (0 to 9), 1.7 at nine months (0 to 9), 1.5 at one year (0 to 8) and 2.0 at mean 46 months (0 to 10)). There was a high correlation (r > 0.7; p < 0.001) between the mean VAS scores for pain and the mean painDETECT scores at three months, one year and three years post-operatively. There was no correlation between the pre-operative scores and any post-operative scores at any time point. We report the prevalence of pain and neuropathic pain at various intervals up to three years after TKR. Neuropathic pain is an underestimated problem in patients with pain after TKR. It peaks at between six weeks and three-months post-operatively. However, from these data we were unable to predict which patients are most likely to be affected.

The safety profile of a retrospective Accessory Postero-Lateral hind foot portal: the risk of sural nerve damage during visualisation of the Achilles tendon insertion

INTRODUCTION

The Accessory Postero-Lateral (AccPL) portal has recently been described to improve the visualisation for the endoscopic debridement of Haglund's tubercle. The safety of using this portal has been considered previously for posterior ankle arthroscopy. We performed a study to determine the proximity of the AccPL portal to the sural nerve.

METHODS

We compared the distances between AccPL and PL portals to the sural nerve in 17 cadaveric specimens.

RESULTS

The AccPL portal was significantly closer (mean 12.0mm, range 6-19 mm, SD=3.64) to the sural nerve than the PL portal (mean 14.1mm, range 11-18 mm, SD=2.34) (t(16)=-2.34, p=0.03). In two cases the sural nerve was in contact with the clip but on close inspection, the nerve had not been damaged in any of the specimens.

CONCLUSIONS

We conclude that the AccPL portal is a safe method to allow visualisation during endoscopic debridement of the Achilles tendon insertion. We also recommend that the portal is used for visualisation rather than instrumentation.

The effects of technology on relatives in critical care environments

Technology has both good and bad effects and is both the cause of and solution to many problems. Demonstrating a clear understanding of and competence with technology is one important way in which staff can foster relatives' confidence and trust. A number of emotional and behavioural responses to technology in spouses are highlighted. Fear, curiosity and security are relevant to relative's perceptions and responses.

Ion channel forming colicins

Entry of proteins into membranes and transmembrane ion channel formation are two fundamental aspects of membrane biology. The ion channel forming colicins beautifully exemplify both properties. Recent results delineate the structure of a whole colicin; coupled with new biophysical studies, a mechanism for insertion is proposed.

Wave-front sensing by pseudo-phase-conjugate interferometry

A wave-front sensor based on pseudo-phase-conjugate interferometry is presented. We show that a pseudo-phase-conjugate interferometer is suitable for the measurement of phase distribution on a propagating wave. This new method may be employed for optical workshop applications and wave-front sensing for adaptive optics. The theoretical sensitivity of the interferometer is twice that of the Hartmann-Shack wave-front sensor. Preliminary laboratory experiments demonstrate excellent performance and consistency with computer simulations.

1.59 A structure of trypsin at 120 K: comparison of low temperature and room temperature structures

The structure of a rat trypsin mutant [S195C] at a temperature of 120 K has been refined to a crystallographic R factor of 17.4% between 12.0 and 1.59 A and is compared with the structure of the D102N mutant at 295 K. A reduction in the unit cell dimensions in going from room temperature to low temperature is accompanied by a decrease in molecular surface area and radius of gyration. The overall structure remains similar to that at room temperature. The attainable resolution appears to be improved due to the decrease in the fall off of intensities with resolution [reduction of the temperature factor]. This decreases the uncertainty in the atomic positions and allows the localization of more protein atoms and solvent molecules in the low temperature map. The largest differences between the two models occur at residues with higher than average temperature factors. Several features can be localized in the solvent region of the 120 K map that are not seen in the 295 K map. These include several more water molecules as well as an interstitial sulfate ion and two interstitial benzamidine molecules.

Saturation site-directed mutagenesis of thymidylate synthase

We have subjected 12 different codons of a synthetic Lactobacillus casei thymidylate synthase (TS) gene to saturation site-directed mutagenesis to create amino acid "replacement sets" at each of those positions. The target residues were chosen because they are highly conserved and because they are important for the structure and function of the protein as indicated by solution and structural studies. The mutagenesis procedure involved excision of a fragment of the synthetic gene containing the target codon, followed by its replacement with a mixture of oligonucleotides which code for all 20 amino acids and the amber stop codon. TS mutants were identified by DNA sequencing, and catalytically active mutants were identified by genetic complementation using a Thy- strain of Escherichia coli. Only 3 of the 12 target amino acids examined were essential for TS activity; and of the 125 total mutants identified, 57 were catalytically active. These results point to a high degree of plasticity of TS in accommodating function with structural change.

Independent mutations at the amino terminus of a protein act as surrogate signals for mitochondrial import

Intracellular delivery of the mitochondrial F1-ATPase beta-subunit precursor from the cytoplasm into the matrix of mitochondria is prevented by deletion of its mitochondrial import signal, a basic amphipathic alpha-helix at its amino terminus. Using a complementation assay, we have selected spontaneous mutations which restore the correct in vivo localization of the protein containing the import signal deletion. Analysis of these mutations revealed that different functional surrogate mitochondrial targeting signals formed within a narrow region of the extreme amino terminus of the import signal deleted beta-subunit. These modifications specifically replace different acidic residues with neutral or basic residues to generate a less acidic amphipathic helix within a region of the protein which is accessible for interaction with the membrane surface. The observations of this study confirm the requirement for amphipathicity as part of the mitochondrial import signal and suggest how mitochondrial targeting signals may have evolved within the extreme amino terminus of mitochondrial proteins.

Purification and crystallization of creatine kinase from rabbit skeletal muscle

Crystallization is the primary rate-limiting step in protein structure determination. It has been our experience over approximately 10 years that crystals are obtained in about 20% of the proteins attempted and that only about 10% of these crystals are sufficiently well ordered to permit atomic resolution structure analysis. In attempts to overcome this limitation, we have investigated the effect on crystallization of microheterogeneity in a protein regarded as pure by conventional criteria. Creatine kinase was purified from rabbit skeletal muscle and crystallized from methylpentanediol. The protein appeared to be nearly pure judging by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and high specific activity. The crystals that were obtained were of poor quality, and an extensive survey of precipitants, crystallization conditions, and additives failed to discover conditions from which usable crystals could be obtained. The enzyme was then subjected to a series of further purification steps. After each purification step, the quality of the crystals obtained under almost identical conditions improved. The final purification step was flat-bed isoelectric focusing. Crystals grown from focused creatine kinase are well ordered and diffract to approximately 3-A resolution.

Parasites and associated pathology observed in cetaceans stranded along the Oregon coast

Ten stranded cetaceans, representing five species, from the Oregon Coast were examined between 1973-1977. Fourteen genera of parasites, together with the pathogenesis and pathology associated with the presence of some of these parasites are reported.

Immune complexes in congenital and natal cytomegalovirus infections of man

The occurrence of circulating immune complexes was investigated in 31 patients with cytomegalovirus infection (29 infected in utero and 2 with natal infection) and 34 uninfected controls. Anti-complementary activity above 1:20 occurred in 34% (29/86) of the sera tested from the infected group in contrast to 7.5% (3/40) in the controls (P < 0.005). When assayed by means of a lymphoblastoid cell line (Raji cell test), the reactivity in these groups was 45 (39/86) and 2.7% (1/36), respectively (P < 0.001). Correlation of results between these two complement-dependent assays occurred in 75% of samples collected from the infected group. Frequency of reactivity was higher in severe intrauterine infection and during the 1st yr of life paralleling the patterns of viral excretion and humoral immune responses. Physicochemical characterization demonstrated that reactive substances in sera were acid-dissociable and, in one sample tested, contained 7S IgG antibodies with cytomegalovirus (CMV) specificity. Circulating immune complexes were heavier (18-22S) in sick, as opposed to subclinically CMV-infected patients, in whom intermediate size complexes (12-16S) were found. In three of four symptomatic patients whose demise was due to severe congenital infection, granular deposits of immunoglobulins and C3 were detected in a pattern typical of immune complexes along the glomerular basal membrane of the glomeruli. Whether or not circulation and deposition of heavier immune complexes contributed to the adverse clinical outcome is unresolved. Because of the high incidence of both congenital and natal CMV infections, definition of the pathogenetic potentials of both heavy and intermediate size immune complexes is required to design more effective therapeutic measures.

C1r deficiency: an inborn error associated with cutaneous and renal disease

The studies of sera from two siblings with C1r deficiency are described. The brother (18 yr old) has shown clinical manifestations resembling lupus erythematosus for 5 yr, and the sister (24 yr old) has had arthralgia and recurrent episodes of rhinobronchitis since early childhood. Three siblings have died: one brother died at age 12 with symptoms similar to the disease of the male patient studied here, and two other siblings died in infancy, probably from infection. The low hemolytic C1 activity of the patients could be restored by the addition of purified C1r to their sera. Bactericidal activity and immune adherence were found to be impaired. When alternate pathways of the complement system were studied, both sera permitted activation of terminal components with endotoxin and cobra venom factor. These findings support the view that an alternate pathway for activation of the terminal portion of the complement cascade exists which does not utilize the conventional pathway operating through the usual early components.