Two models for outcome prediction - a comparison of logistic regression and neural networks

OBJECTIVES

Accurately predicting disease progress from a set of predictive variables is an important aspect of clinical work. For binary outcomes, the classical approach is to develop prognostic logistic regression (LR) models. Alternatively, machine learning algorithms were proposed with artificial neural networks (ANN) having become popular over the last decades. Although some studies have compared predictive accuracies of LR and ANN models, some concerns regarding their methodological quality have been voiced. Our comparison has the advantage of being based on two large independent data sets allowing for elaborate model development and independent validation.

METHODS

From the German Stroke Database, a learning data set including 1754 prospectively recruited patients with acute ischemic stroke was used. Utilizing LR and ANN, two prognostic models were developed predicting restitution of functional independence and survival after 100 days. The resulting models were applied to classify 1470 patients with acute ischemic stroke; this test data set was collected independently from the learning data. Error fractions in the test data were determined, and differences in error fractions between the algorithms were calculated with 95% confidence intervals.

RESULTS

For most prognostic models, error fractions in the test data were below 40%. There was no difference between the algorithms except for the model predicting completely versus incompletely restituted or deceased patients (difference in error fractions = 4.01% [2.10-5.96%], p = 0.0001).

CONCLUSIONS

The conscientiously applied LR remains the gold standard for prognostic modelling; however, ANN can be an alternative automated "quick and easy" multivariate analysis.

Efficacy and safety of 6.25 mg t.i.d. feverfew CO2-extract (MIG-99) in migraine prevention--a randomized, double-blind, multicentre, placebo-controlled study

The efficacy and tolerability of a CO(2)-extract of feverfew (MIG-99, 6.25 mg t.i.d.) for migraine prevention were investigated in a randomized, double-blind, placebo-controlled, multicentre, parallel-group study. Patients (N = 170 intention-to-treat; MIG-99, N = 89; placebo, N = 81) suffering from migraine according to International Headache Society criteria were treated for 16 weeks after a 4-week baseline period. The primary endpoint was the average number of migraine attacks per 28 days during the treatment months 2 and 3 compared with baseline. Safety parameters included adverse events, laboratory parameters, vital signs and physical examination. The migraine frequency decreased from 4.76 by 1.9 attacks per month in the MIG-99 group and by 1.3 attacks in the placebo group (P = 0.0456). Logistic regression of responder rates showed an odds ratio of 3.4 in favour of MIG-99 (P = 0.0049). Adverse events possibly related to study medication were 9/107 (8.4%) with MIG-99 and 11/108 (10.2%) with placebo (P = 0.654). MIG-99 is effective and shows a favourable benefit-risk ratio.

[Treatment and prophylaxis for cluster headaches and other trigeminal autonomic headaches. Revised recommendations of the German Migraine and Headache Society]

Following the new IHS classification, cluster headache, paroxysmal hemicrania, and short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT syndrome) are included in the classification as trigeminal autonomic cephalgias (TAC). The similarities of these syndromes suggest a considerable shared pathophysiology. These syndromes have in common that they involve activation of trigeminovascular nociceptive pathways with reflex cranial autonomic activation. Clinically, this physiology predicts pain with some combination of lacrimation, conjunctival injection, nasal congestion, or eyelid edema. Broadly the management of TAC comprises acute and prophylactic treatment. Some types of trigeminal autonomic headaches such as paroxysmal hemicrania and hemicrania continua have, unlike cluster headaches, a very robust response to indomethacin, leading to a consideration of indomethacin-sensitive headaches. This review covers the clinical picture and therapeutic options. Although studies following the criteria of evidence-based medicine (EBM) are rare, most patients can be treated sufficiently.

Medication overuse headache: rates and predictors for relapse in a 4-year prospective study

We present a prospective 4-year follow-up study of 96 patients with medication overuse headache following withdrawal. Complete datasets were available from 85 patients (89%) 6 months, from 79 patients (82%) 1 year and from 75 patients (78%) 4 years after withdrawal. Twenty-six patients (31%) relapsed within the first 6 months after withdrawal. The number of relapses increased to 32 (41%) 1 year and to 34 (45%) 4 years after withdrawal. The 4-year relapse rate was lower in migraine than in tension-type headache (32% vs. 91%, P<or=0.001) and combination of migraine and tension-type headache (32% vs. 70%, P<or=0.027) and also lower in patients overusing triptans than analgesics (21% vs. 71%, P<or=0.001). The study suggests that the majority of relapses occur within the first year after withdrawal and that the long-term success of withdrawal depends on the type of primary headache and the type of overused medication.

Clinical features and therapy of medication overuse headache

Inappropriate use of headache medication (>15 times/month) for the treatment of headache episodes may contribute to the development of chronic headache which is refractory to most treatments. Physicians experienced in the treatment of migraine and other headaches are well aware that the daily intake of antipyretic or antiinflammatory analgesics, opioids, ergot alkaloids and "triptans" may result in chronic daily headache. Conversely, if a patient complains of chronic headache and takes pain medication every day, this headache is most likely to be caused and sustained by the medication and will vanish or improve with abstinence. Treatment includes drug withdrawal followed by structured acute therapy and initiation of migraine prophylactic treatment.

Presumed pharmacologically induced change from upbeat- to downbeat nystagmus in a patient with Wernicke’s encephalopathy

A case of Wernicke's encephalopathy due to proven thiamine deficiency suffering from upbeat nystagmus (UN) changing to downbeat nystagmus (DN) after a latency of 1 year is presented. The case was also notable for the finding of positive oligoclonal bands in the CSF. The underlying pathophysiological mechanisms and a possible effect of baclofen treatment are discussed.

No effect of eletriptan administration during the aura phase of migraine

Migraine aura is a warning sign readily recognized by patients. From the onset of aura it takes 30-60 min before the headache phase starts. Administration of acute medication during aura should provide sufficient time to achieve therapeutic plasma levels, counteracting the headache. To test this hypothesis we evaluated the efficacy of eletriptan 80 mg taken during aura. Patients met International Headache Society diagnostic criteria for migraine with aura, with an attack frequency of at least one per month and with aura occurring in > 50% of recent attacks. Of 123 patients randomized, 87 (71%) were treated with a double-blind, one attack, during the aura phase before headache, dose of either eletriptan 80 mg (n = 43; 74% female; mean age, 40 years), or placebo (n = 44; 82% female; mean age, 40 years). The primary outcome measure was the proportion of patients not developing moderate-to-severe headache within 6 h post-dose. There was no significant difference in the proportion of patients developing moderate-to-severe headache on eletriptan (61%) versus placebo (46%). Eletriptan was well tolerated and did not prolong the aura phase. Typical transient triptan adverse events were observed; most were mild-to-moderate in intensity. This study confirms the findings of two studies showing that triptans are ineffective but safe when given during the migraine aura phrase.

[Treatment and prophylaxis of an acute migraine attack]

The treatment of migraine takes into consideration the intensity of the headache and the accompanying symptoms. The goal is to reduce the headache intensity, to relieve nausea and vomiting and to restore the ability to function in the daily routine. For drug treatment, there are now highly effective serotonin agonists available in addition to the older ergotamine preparations. A problem with all migraine analgesics is that in long lasting migraine attacks, the headache can recur as the pharmacological effect of the medication wears off. Through nonmedicinal and medicinal prophylactic measures, the frequency and intensity of the migraine attacks can be reduced. Keeping a headache diary for documentation is essential.

Schneller, h�her, weiter

In the past months significant new data have been published in the field of headache and migraine. With the publication of the second and revised version of the classification of headache disorders, new entities such as chronic migraine have been introduced. Moreover, the repertoire of drugs available for the treatment of migraine has changed as well. Whereas ergot derivatives have been almost completely taken off the market, seven triptans in 23 different preparations are now available and allow the physician to customize the treatment of acute attacks. CGRP antagonists, a completely new generation of anti-migraine compounds for the treatment of acute attacks, have now been tested successfully in clinical trials. For the prophylaxis of migraine, several agents that had been well established for decades have recently been taken off the market too, but new agents such as topiramate, which possesses different modes of action, have been tested successfully and are now available for the prophylaxis of migraine. The following review will summarize the newest developments in acute therapy and prophylactic treatment of migraine.

Empfehlungen zur Statintherapie im Alter

Elderly patients are significantly less likely to receive statins than younger patients possibly because of doubts regarding compliance or concerns regarding the increased likelihood of adverse events and drug interactions. Poor compliance can be expected especially in patients suffering from dementia or depression as well as those whose stage of cardiovascular disease exhibits few symptoms. On the other hand, the clinical significance of CHD events is high in the elderly, and 80% of coronary deaths occur in patients aged over 65 years. The average statistical life expectancy of elderly and old patients is often underestimated. The HPS and PROSPER studies showed that statins reduce mortality and morbidity even in very elderly individuals with a high global cardiovascular risk and/or CAD. Patients up to the age of 79 years should be treated according to the same guidelines as younger patients. Statin therapy should only be considered for patients aged 80 years and older who are at a very high risk for cardiovascular events.

The therapeutic profile of zolmitriptan in clinical practice

The efficacy and tolerability of the 5-HT1B/1D-receptor agonist zolmitriptan was evaluated in an open post-marketing surveillance study in 12,919 patients, treating 36,510 migraine attacks. Mean visual analogue scale scores for pain decreased (6.9-2.2; 68% improvement) and scores for impairment of normal activities decreased (6.6-2.2; 67% improvement) at 2 h after dose. Non-headache symptoms of migraine resolved in 73-86% of attacks. Improvement was achieved within 2 h in >80% of attacks and within 1 h in 37% of attacks. This high level of efficacy was achieved with a single 2.5 mg dose in 95% of attacks. Compared with previous migraine treatments, 85% of patients preferred zolmitriptan for efficacy and 56% for better tolerability. Corresponding preference rates were 87 and 63% when compared with ergot alkaloids. Adverse events occurred in 2% of patients and were either typical class effects or known symptoms and complications of migraine. These results provide evidence for the high efficacy and good tolerability of the 2.5 mg dose of zolmitriptan in clinical practice in migraine. Zolmitriptan was very well tolerated, with patients expressing a distinct preference for zolmitriptan over previous treatments.

Efficacy of 1,000 mg Effervescent Acetylsalicylic Acid and Sumatriptan in Treating Associated Migraine Symptoms

Recently a new effervescent acetylsalicylic acid (ASA) tablet with high buffering capacity has been developed. In this double-blind, 3-arm, multicenter, parallel-group study, 433 patients were treated either with 1,000 mg effervescent ASA or 50 mg encapsulated sumatriptan or placebo. The primary endpoint was the percentage of patients with complete remission of the 3 accompanying symptoms nausea, photophobia and phonophobia within 2 h after intake of the study drug. 43.8% of patients treated with ASA, 43.7% of patients treated with sumatriptan and 30.9% of patients treated with placebo showed complete remission of all 3 accompanying symptoms (p < 0.05 for ASA and sumatriptan vs. placebo). Both active treatments were superior to placebo regarding the individual symptoms photophobia and phonophobia, but not for nausea. The percentage of patients with reduction in headache severity from moderate or severe to mild or no pain (secondary objective) was 49.3% for ASA, 48.8% for sumatriptan and 32.9% for placebo. All active treatments were superior to placebo (p < 0.05). 25.3, 24.4 and 14.5% of patients treated with ASA, sumatriptan or placebo were pain free at 2 h. Drug-related adverse events were reported in 3.9, 4.7 and 6.7% of patients treated with placebo, ASA or sumatriptan. The study showed that administration of effervescent ASA leads to remission of the migraine symptoms nausea, photophobia and phonophobia, reduces migraine headache and is comparable to sumatriptan.

Use of sequence information in associative learning in control subjects and cerebellar patients

Previous studies of our group have shown that cerebellar patients are impaired in their ability to associate a color and a numeral or two colors with a button push. The aim of the present study was to examine whether control subjects make use of sequence information in visuomotor associative learning tasks and if this ability is impaired in cerebellar patients. A group of eight patients with degenerative cerebellar disease and eight age, sex and IQ matched controls were tested. Subjects had to learn the association between pairs of colored squares and a button push. Two colored squares were shown one after the other in a fixed or random order on a computer screen. Control subjects but not cerebellar patients took advantage of the fixed order information of colored squares in order to improve associative learning. Differences between groups could not be explained by differences in verbal and visuospatial short-term memory, color discrimination, affective state or motor disturbances. Results suggest that impaired sequencing of sensory stimuli may contribute to disorders in visuomotor associative learning in cerebellar patients.

[Recent new information on epidemiology of headache]

We reviewed the epidemiology of headache disorders for the most frequent primary headache-syndromes: migraine, tension-type headache and trigemino-autonomic headache syndromes. In the last years scientific data about headache disorders have increased. New studies investigated not only the prevalence of headaches, but also economic costs of this disorder. Epidemiologic headache research also investigates the quality of life.

Adult post-infectious thalamic encephalitis: acute onset and benign course

We report on two young patients with an encephalitic syndrome and bilateral thalamic lesions following a presumably viral or mycoplasma respiratory tract infection with the main clinical symptoms of organic psychosis in the first and a prolonged amnestic syndrome and ataxia in the second case. Four months later the patients had recovered clinically and the thalamic lesions had resolved on magnetic resonance imaging in one case and almost completely in the other. We interpret the patients' illness as rare cases of a post-infectious acute thalamic encephalitis in adults. The cases and their relationship to possible post-infectious autoimmune inflammatory or toxic pathophysiological mechanisms are discussed and a review of the literature is provided.

Comparative efficacy of eletriptan and zolmitriptan in the acute treatment of migraine

Eletriptan 40 mg and 80 mg have shown greater efficacy in acute migraine than oral sumatriptan 100 mg and naratriptan 2.5 mg. This study continues the systematic series of active comparator trials in the eletriptan clinical development programme. In a multicentre double-blind, double-dummy, parallel-groups trial, 1587 outpatients with migraine by IHS criteria were randomised in a 3: 3 : 3: 1 ratio to eletriptan 80 mg, eletriptan 40 mg, zolmitriptan 2.5 mg or placebo. Of these, 1312 treated a single migraine attack and recorded baseline and outcome data to be included in the intention-to-treat population. The primary analysis was between eletriptan 80 mg and zolmitriptan. For the primary efficacy end-point of 2-h headache response, rates were 74% on eletriptan 80 mg, 64% on eletriptan 40 mg, 60% on zolmitriptan (P < 0.0001 vs. eletriptan 80 mg) and 22% on placebo (P < 0.0001 vs. all active treatments). Eletriptan 80 mg was superior to zolmitriptan on all secondary end-points at 1, 2 and 24 h, in most cases with statistical significance. Eletriptan 40 mg had similar efficacy to zolmitriptan 2.5 mg in earlier end-points, and significantly (P < 0.05) lower recurrence rate and need for rescue medication over 24 h. All treatments were well tolerated; 30-42% of patients on active treatments and 40% on placebo reported all-causality adverse events that were mostly mild and transient. On patients' global ratings of treatment, both eletriptan doses scored significantly better than zolmitriptan.