Estimates of the virological benefit of antiretroviral therapy are both assay- and analysis-dependent

OBJECTIVE

To assess the potential discrepancies in reported changes in plasma viral load (PVL) depending on how values below the detection limit of the assay are handled in the data analysis phase of a randomized controlled clinical trial.

DESIGN

Data from a recently completed clinical trial comparing combinations of zidovudine, didanosine and nevirapine were analysed. In this trial, PVL was measured using an assay with a lower quantification limit of 400 HIV-1 RNA copies/ml initially. All PVL values less than 500 copies/ml were retested with a more sensitive assay with a lower quantification limit of 20 copies/ml.

METHODS

Several summary measures for assessing change in PVL were calculated using three different methods to adjust for PVL values less than the quantification limit of the assay. The differences between these measures were evaluated.

RESULTS

We found that the magnitude of the discrepancy between summary measures used to report changes in PVL depended on the proportion of subjects with PVL less than the quantification limit of the assay, how those observations were handled in the data analysis, and the relative difference between the quantification limits of the conventional and more sensitive assay.

CONCLUSION

The lack of consensus in reporting of PVL data in the literature makes the interpretation of published trial results difficult. In the absence of agreement on the most appropriate summary measure of PVL data, we recommend that all summaries include information on the quantification limit of the assay used, the proportion of observations at or below the quantification limit and how these observations were handled in the data analysis.

Phase 2 studies of adenosine cardioplegia

BACKGROUND

Laboratory evidence supports the use of adenosine-supplemented cardioplegia. An initial phase 1 dose-ranging clinical evaluation demonstrated that an adenosine concentration of 15 mumol/L could be safely administered with warm blood cardioplegia and suggested that phase 2 studies were warranted.

METHODS AND RESULTS

Two separate double-blind, randomized, placebo-controlled trials were performed in patients undergoing primary, isolated, nonemergent coronary artery bypass graft surgery. Patients were randomized to receive adenosine 15 mumol/L versus placebo in the first study (n = 200) and adenosine 50 or 100 mumol/L versus placebo in the second study (n = 128). Adenosine was infused with both initial and final doses of warm antegrade blood cardioplegia. The data from the 2 trials were combined using the methods of Mantel and Haenszel, and the results of the meta-analysis are presented as the relative risk with their associated 95% confidence intervals (CI). The different study groups were comparable with respect to all preoperative clinical characteristics, angiographic findings, and intraoperative variables. In both trials 1 and 2, no differences were found between groups in the incidence of the individual primary or secondary outcomes. Similarly, when both studies were combined, there was no significant evidence of any consistent treatment benefit (primary: death: relative risk [RR] = 1.02, 95% CI = 0.06, 16.6; myocardial infarction by CK-MB: RR = 0.84, CI = 0.54, 1.31; low output syndrome: RR = 1.38, CI = 0.29, 6.42; any of the above: RR = 0.98, CI = 0.78, 1.25; secondary: Q-wave myocardial infarction: RR = 1.30, CI = 0.41, 4.13; myocardial infarction by troponin T: RR = 0.7, CI = 0.40, 1.21; inotrope requirement: RR = 0.9, CI = 0.46, 1.79; intra-aortic balloon pump requirement: RR = 0.6, CI = 0.07, 4.81; P > 0.20).

CONCLUSIONS

Despite promising experimental data, adenosine supplementation of warm blood cardioplegia did not demonstrate any statistically significant benefit in patients undergoing elective coronary artery bypass graft surgery. Although sample sizes were relatively small, based on our interim analyses, it is unlikely that increased patient enrollment would reveal any substantive clinical differences between groups.

Hormone-dependent regulation of GABAA receptor gamma subunit mRNAs in sexually dimorphic regions of the rat brain

Transmission mediated by gamma-aminobutyric acid type A (GABAA) receptors expressed within the medial preoptic area (mPOA) and the ventromedial nucleus (VMN) of the hypothalamus is known to play critical, but contrasting, roles in regulating steroid-dependent sexual behaviours in rats. Previous studies have demonstrated a striking dichotomy in receptor composition between the two regions with regard to gamma, but not alpha or beta, subunit expression. To test if gonadal steroids regulate the expression of the gamma subunit genes within the mPOA and the VMN, in situ hybridization analysis for messenger RNAs encoding the gamma 1, gamma 2Short (gamma 2S) and gamma 2Long (gamma 2L) subunits was done in gonadectomized male and female rats and in gonadally intact females over the oestrous cycle. No significant differences in the expression of the gamma subunit mRNAs were observed in gonadectomized male versus female rats. Significant effects of gonadal state in female rats were observed for gamma 1 mRNA levels in the mPOA and gamma 2L levels in the VMN. These data demonstrate that gonadal hormones exert activational control of expression of GABAA receptor gamma subunit mRNAs and suggest that differences in receptor structure may contribute to the functional modulation of female sexual behaviours mediated by GABAergic transmission in these regions.

Suppression of plasma viral load below 20 copies/ml is required to achieve a long-term response to therapy

BACKGROUND

Current guidelines state that the goal of antiretroviral therapy for HIV-infected individuals is to suppress plasma viral load (pVL) to below 400 copies/ml.

METHODS

Predictors of achieving and maintaining pVL suppression were examined in a randomized trial of combinations of zidovudine, nevirapine and didanosine in patients with CD4+ T cell counts of between 200 and 600 x 10(6) cells/l who were naive to antiretroviral therapy and AIDS-free at enrolment.

RESULTS

One hundred and four patients had pVL > 500 copies/ml at baseline and a pVL nadir below 500 copies/ml. Of these, 77 patients experienced an increase in pVL above 500 copies/ml. The median number of days of pVL suppression to below 500 copies/ml was 285 (42) for patients with pVL nadir < or = (>) 20 copies/ml (P = 00.0001). The relative risk of an increase in pVL above 500 copies/ml associated with a pVL nadir below 20 copies/ml was 0.11 (P = 0.0001). The relative risks of an increase in pVL above 5000 copies/ml associated with a pVL nadir below 20 copies/ml or between 20 and 400 copies/ml were 0.05 [95% confidence interval (CI), 0.02-0.12] and 0.37 (95% CI, 0.23-0.61) respectively, compared with individuals with a pVL nadir > 400 copies/ml. Individuals with a pVL nadir < or = 20 copies/ml were at a significantly lower risk of virologic failure than individuals with a pVL nadir of between 21 and 400 copies/ml (P = 0.0001).

CONCLUSIONS

Our results demonstrate that suppression of pVL below 20 copies/ml is necessary to achieve a long-term antiretroviral response. Our data support the need for a revision of current therapeutic guidelines for the management of HIV infection.

Induction-maintenance antiretroviral therapy: proof of concept

OBJECTIVE

To investigate the concept of aggressive initial combination therapy followed by reduction to a less demanding maintenance regimen with respect to its potential for sustaining viral suppression.

DESIGN

Durable viral suppression to < 20 HIV RNA copies/ml plasma was achieved with zidovudine-nevirapine-didanosine (ZDV-NVP-ddl) therapy. Potential for sustained antiviral response was explored for patients who began with ZDV-NVP-ddl and subsequently interrupted ddl.

METHODS

Antiretroviral-naive patients were treated with ZDV-NVP, ZDV-ddl, or ZDV-NVP-ddl. Viral load was measured with the Amplicor assay (limit of quantification 400 copies/ml) and by the Ultra Direct assay (limit of quantification 20 copies/ml) when the Amplicor result was < 500 copies/ml. Treatment adherence for each drug was recorded, including all dose adjustments.

RESULTS

Five patients who had begun treatment with ZDV-NVP-ddl discontinued ddl for at least 6 weeks after achieving viral load levels below detection. All were documented to have sustained their viral load at < 20 copies/ml during the ddl interruption. Two patients permanently discontinued ddl, both with sustained viral load below detection for more than 1 year while treated with ZDV NVP. In contrast, no patient initially receiving ZDV-NVP was able to maintain viral load below detection for sustained periods; none had viral load below detection after week 12 of treatment.

CONCLUSIONS

After induction with ZDV-NVP-ddl, patients were able to sustain viral suppression with a regimen (ZDV NVP) that was only transiently effective as initial therapy. There was no evidence of virologic escape, even with the most sensitive measure of plasma viral load.

A randomized, double-blind trial comparing combinations of nevirapine, didanosine, and zidovudine for HIV-infected patients: the INCAS Trial. Italy, The Netherlands, Canada and Australia Study

CONTEXT

Current guidelines recommend that individuals infected with the human immunodeficiency virus type 1 (HIV-1) be treated using combinations of antiretroviral agents to achieve sustained suppression of viral replication as measured by the plasma HIV-1 RNA assay, in the hopes of achieving prolonged remission of the disease. However, until recently, many drug combinations have not led to sustained suppression of HIV-1 RNA.

OBJECTIVE

To compare the virologic effects of various combinations of nevirapine, didanosine, and zidovudine.

DESIGN

Double-blind, controlled, randomized trial.

SETTING

University-affiliated ambulatory research clinics in Italy, the Netherlands, Canada and Australia (INCAS).

PATIENTS

Antiretroviral therapy-naive adults free of the acquired immunodeficiency syndrome with CD4 cell counts between 0.20 and 0.60x10(9)/L (200-600/microL).

INTERVENTION

Patients received zidovudine plus nevirapine (plus didanosine placebo), zidovudine plus didanosine (plus nevirapine placebo), or zidovudine plus didanosine plus nevirapine.

MAIN OUTCOME MEASURE

Plasma HIV-1 RNA.

RESULTS

Of the 153 enrolled patients, 151 were evaluable. At week 8, plasma HIV-1 RNA levels had decreased by log 2.18, 1.55, and 0.90 in the triple drug therapy, zidovudine plus didanosine, and zidovudine plus nevirapine groups, respectively (P<.05). The proportions of patients with plasma HIV-1 RNA levels below 20 copies per milliliter at week 52 were 51%, 12%, and 0% in the triple drug therapy, zidovudine plus didanosine, and zidovudine plus nevirapine groups, respectively (P<.001). Viral amplification was attempted in 59 patients at 6 months. Viral isolation was unsuccessful in 19 (79%) of 24, 10 (53%) of 19, and 5 (31%) of 16 patients in the triple drug therapy, zidovudine plus didanosine, and zidovudine plus nevirapine groups, respectively. Among patients from whom virus could be amplified, resistance to nevirapine was found in all 11 patients receiving zidovudine plus nevirapine and in all 5 patients receiving triple drug therapy. Rates of disease progression or death were 23% (11/47), 25% (13/53), and 12% (6/51) for the zidovudine plus nevirapine, zidovudine plus didanosine, and triple drug therapy groups, respectively (P=.08).

CONCLUSIONS

Triple drug therapy with zidovudine, didanosine, and nevirapine led to a substantially greater and sustained decrease in plasma viral load than the 2-drug regimens studied. Our results also suggest that suppression of viral replication, as demonstrated by a decrease in the plasma HIV-1 RNA load below the level of quantitation of the most sensitive test available, may at least forestall the development of resistance.

Patterns of compliance with once versus twice daily antihypertensive drug therapy in primary care: a randomized clinical trial using electronic monitoring

OBJECTIVE

To evaluate patterns of compliance with once versus twice daily administration of antihypertensive therapy (primary-outcome measure) and relevance of partial compliance for blood pressure control (secondary outcome measure).

DESIGN

Multicentre, nonblinded, parallel group randomized design.

SETTING

Nonacademic primary care practices across Canada.

STUDY POPULATION

Patients with mild essential hypertension (diastolic blood pressure 95 to 110 mmHg) of either sex (40% women), age 18 to 80 years (average 55 years). One hundred and ninety-eight patients were randomized to active treatment; 14 patients discontinued the study because of side effects.

INTERVENTIONS

After a four-week placebo run-in period, patients were randomized to amlodipine 5 mg once-a-day or diltiazem slow release formulation (SR) 90 mg twice daily. Doses were increased to 10 mg and 180 mg to achieve sitting diastolic blood pressure of 90 mmHg or less.

OUTCOME MEASURE

During 20 weeks on active treatment, compliance was assessed by pill counts and medication event monitoring system (MEMS), assessing percentage of prescribed doses taken, percentage days correct doses taken, percentage prescribed doses taken on time and blood pressure control as determined by office blood pressure measurement.

RESULTS

The percentage prescribed doses taken (by either pill count of MEMS) showed a high degree of compliance, similar for the two treatments. However, other parameters of compliance were significantly better with once versus twice daily therapy. Partial compliance (less than 80% by pill count) led to less blood pressure control with the short acting diltiazem, but did not affect blood pressure control for the long acting amlodipine. Side effects profiles did not differ between the two treatments.

CONCLUSIONS

Within the constraints of a clinical trial, hypertensive patients in primary care show a high degree of overall compliance with once or twice daily pill-taking, but patterns of pill-taking are more erratic with twice versus once daily medication, particularly in men. The results suggest that the negative consequences of partial compliance for blood pressure control can be offset by choosing agents with a duration of action well beyond the dosing interval.

The appearance of inverted Meckel diverticulum with intussusception on air enema

This paper presents the appearances of inverted Meckel diverticulum with an irreducible intussusception on air enema in four children. The inverted Meckel diverticulum appeared as a bulbous (3) or triangular (1) filling defect in the air column projecting off the distal end of the soft tissue mass of the irreducible intussusceptum. The bulbous defect appears to be highly suggestive, and may be specific, for inverted Meckel diverticulum. Earlier recognition of the presence of the Meckel diverticulum as the lead point of the intussusception could have changed the management in two of the children.

Diet and infant behavior

We studied 142 preterm infants (mean gestation 31 weeks, mean birthweight 1364 g) fed prospectively varied protein and energy intakes. Infants were grouped as either slow or rapid growers based on rate of weight gain. Rapid growers had increased heart rates (166 vs 160 beats/min), respiratory rates (55.7 vs 53.9 bpm), energy expenditure (64.8 vs 61.6 kcal kg(-1) day(-1)), urinary C-peptide levels (1.59 vs 0.79 ng ml(-1)) and time in active sleep (78.0 vs 75.2%), and decreased spectral edge frequency in the electroencephalogram (2.96 vs 4.45 Hz) compared to slow growers. We conclude that preterm infants growing at varying rates manifest physiological and behavioral differences, and that these patterns may reflect altered autonomic balance.

Effect of 10 percent carbamide peroxide on color of provisional restoration materials

To improve esthetic results, nightguard vital bleaching of teeth using 10 percent carbamide peroxide, or CP, may be indicated when an anterior tooth is restored with a provisional crown. This study evaluated the effect of NGVB solutions containing 10 percent CP on the color stability of provisional restoration materials. Disks were fabricated from six representative provisional restoration materials and were tested in five different 10 percent CP bleaching agents. An orange discoloration occurred with provisional materials that contained methacrylate when they were exposed to 10 percent CP bleaching solutions.

Sonographic appearances of inverted Meckel diverticulum with intussusception

This study illustrates the sonographic findings of inverted Meckel diverticulum acting as a lead point of an intussusception in five patients. In four patients, the inverted diverticulum was seen as a segment of blind-ending, thick-walled bowel projecting for a variable distance from the apex of the intussusceptum. The larger diverticula had a characteristic bulbous shape. The central serosal surface of the inverted diverticulum was filled with fluid in one patient, with fluid and fat in another, and with echogenic fat only in the other two. The presence of fat was confirmed by CT in one patient. The features illustrated in these four patients appear to be specific. In the fifth patient, the sonogram revealed a nonspecific echogenic mass at the apex of the intussusceptum. Recognition of these features on sonography may obviate the need for further investigation.

Influence of gender, race, and education on patient preferences and receipt of cardiac catheterizations among coronary care unit patients

The extent to which a preference for less aggressive care explains the lower rate of invasive cardiac services for women and African-Americans is unknown. A prospective observational study of 272 patients admitted to the coronary care unit was conducted at a tertiary referral teaching hospital and a community teaching hospital. In stepwise multivariate analysis, having less than a college education, poor cardiac function, not having undergone a previous cardiac catheterization, being a patient in a nonreferral community hospital, and current smoking were positively associated with a patient's stating that he or she would disagree with a physician's recommendation for a cardiac catheterization. The step-wise multivariate model with cardiac catheterization as the dependent variable indicated that being a patient in a referral medical center, patient willingness to accept a physician's recommendation for a cardiac catheterization, severe heart disease, and having attended high school were predictive. Women did not differ from men in their preference for or receipt of cardiac catheterization. Patients in the coronary care unit with lower levels of education were less likely to undergo cardiac catheterization. This association was only partly explained by less educated patients' being less willing to accept a physician's recommendation to undergo cardiac catheterization.

Nevirapine, zidovudine, and didanosine compared with zidovudine and didanosine in patients with HIV-1 infection. A randomized, double-blind, placebo-controlled trial. National Institute of Allergy and Infectious Diseases AIDS Clinical Trials Group Protocol 241 Investigators

OBJECTIVE

To study the addition of a third human immunodeficiency virus type 1 (HIV-1) reverse transcriptase inhibitor, nevirapine, to the combination of zidovudine and didanosine.

DESIGN

A 48-week, randomized, double-blind, placebo-controlled trial at 16 AIDS (acquired immunodeficiency syndrome) Clinical Trials Units.

PATIENTS

398 adults who had HIV-1 infection, had 350 or fewer CD4+ T lymphocytes/mm3, and had had more than 6 months of previous nucleoside therapy.

INTERVENTION

1) Either nevirapine or placebo (200 mg/d for 2 weeks, then 400 mg/d thereafter) and 2) open-label zidovudine (600 mg/d) and didanosine (400 mg/d for patients weighing > or = 60 kg).

MEASUREMENTS

CD4+ T lymphocyte counts, time to first HIV-1 disease progression event or death, adverse events, and nevirapine levels in plasma samples taken at random were measured in all patients. Plasma levels of HIV-1 RNA HIV-1 infectivity titer in peripheral blood mononuclear cells; serum p24 antigen levels; and plasma levels of zidovudine and didanosine were measured in patients enrolled at half the study sites.

RESULTS

After 48 weeks of study treatment the patients assigned to the triple-combination regimen (nevirapine, zidovudine, and didanosine) had an 18% higher mean absolute CD4 cell count (95% Cl, 7% to 29%; P = 0.001), a 0.32 log10 lower mean infectious HIV-1 titer in peripheral blood mononuclear cells (Cl, 0.05 to 0.59 log10 infectious units per million cells; P = 0.023), and a 0.25 log10 lower mean plasma HIV-1 RNA level (Cl, 0.03 to 0.48 log10 RNA copies/mL; P = 0.028) than did patients assigned to the double-combination regimen (zidovudine and didanosine). Severe rashes were more common among patients assigned to receive the triple combination (9% compared with 2%; P = 0.002). Risk for disease progression did not differ between the two groups (relative hazard of the triple-combination group, 1.24 [Cl, 0.75 to 2.06]; P > 0.2), although the study had only moderate power to detect a major difference.

CONCLUSIONS

Adding nevirapine to zidovudine and didanosine improved the long-term immunologic and virologic effects of therapy and was associated with severe rash among the patients studied, who had had extensive previous therapy. These results support 1) the continuing development of combinations of more than two antiretroviral drugs to increase and prolong HIV-1 suppression and 2) the potential utility of nevirapine in combination regimens.

Smiling and fussing in seven-month-old preterm and full-term black infants in the still-face situation

We investigated emotional responses to the still-face paradigm in 7-month-old preterm and full-term black infants. Baby FACS criteria were used to code the duration and intensity of infant smiles and the presence or absence of cry faces and fussy vocalizations within each episode. Infants in both groups showed the still-face effect: a significant reduction in smiling from episode 1 (baseline) to episode 2 (maternal still-face) and partial return to baseline in episode 3 (recovery). A multivariate analysis of covariance (MANCOVA) for big smiles yielded significant main effects for group and episode and a significant group x episode interaction. Preterm infants spent less time than full-term infants displaying big smiles in episode 1 and a less pronounced decrease in big smiles in episode 2. Maternal depressive symptoms did not differ significantly between groups. Counter to our expectations, depressive symptoms were positively associated with small-to-medium smiles in the baseline episode but not with big smiles in any episode. These findings confirm the robustness of the still-face paradigm and its potential usefulness for research on individual as well as group differences in affective communication in infants.

Penetration of the holmium:YAG laser through fluid

PURPOSE

The 2.1-microns pulsed holmium:yttrium-aluminum-garnet (Ho:YAG) laser combines the properties of transmissibility down a flexible silica fiber, enabling percutaneous or endoscopic use, with high water absorption, suggesting good safety characteristics. Laser attenuation in practice, however, is an extremely complex process. The authors studied its effective penetration through blood, bile, urine, saline, and contrast media.

MATERIALS AND METHODS

With use of a fiberoptically directed beam and a laser power meter, penetration was measured in vitro with the fiber tip separated from the medium by 5 cm (noncontact mode) and with the fiber tip immersed (contact mode). Logarithm of energy falloff was measured against fluid thickness. Attenuation coefficients (mu) and half value layer (HVL) distances (estimated thickness of fluid needed to have power) were measured.

RESULTS

In noncontact mode, power falloff was exponential. Non-sanguinous media had similar values for mu and HVL (mu = 2.24-2.70 mm-1 and HVL = 0.26-0.31 mm) close to theoretical predictions. Blood caused significantly (P < .05) more attenuation (mu = 5.15 mm-1, HVL = 0.13 mm). In contact mode, attenuation was much more complex with "plateau" distances of up to 1.2 mm, below which attenuation was negligible. The HVL distances ranged from 0.9 to 1.8 mm and were up to 14 times higher. The main reason is probably the formation of microcavities around the fiber tip.

CONCLUSION

The effective penetration of this laser when immersed may be several times that predicted, with important clinical implications.