Neurosyphilis: A Current Review

Multicentric evaluation of a specific intrathecal anti-Treponema pallidum IgG index as a diagnostic biomarker of neurosyphilis: results from a retro-prospective case-control study

BACKGROUND AND OBJECTIVES

The diagnosis of neurosyphilis (NS) lacks a true 'gold standard', making the diagnosis challenging while consequences of a misdiagnosis are potentially severe. The aim of this study was to evaluate the diagnostic performance of measuring an antibody index (AI) for the intrathecal synthesis of specific anti-Treponema pallidum (T. pallidum) IgG for the diagnosis of NS.

METHODS

Specific anti-T. pallidum IgG were measured simultaneously in paired cerebrospinal fluid (CSF)-serum samples collected retrospectively and prospectively between 2007 and 2022, from patients suspected of NS, in Switzerland. An AI was calculated to account for blood-brain barrier integrity. Area under the receiver operating characteristic curve, sensitivity/specificity and positive/negative predictive values of AI test were estimated. Two NS definitions were used: NS1 included patients with NS suspicion presenting with neurological symptoms and/or acute neurosensory signs, and positive T. Pallidum Hemagglutinations Assay (TPHA)/T. pallidum particle agglutination assay (TPPA) serology and CSF-TPHA/TPPA ≥320, and either CSF-leucocytes >5 cells/mm3 and/or CSF-protein >0.45 g/L and/or a reactive CSF-venereal disease research laboratory (VDRL)/rapid plasma reagin (RPR) test. NS2 included patients with suspected NS presenting with acute ocular and/or otologic symptoms, and positive TPHA/TPPA serology, and a favourable response to NS treatment. Controls were patients diagnosed with any other central nervous system (CNS) pathologies and with positive TPHA/TPPA serology.

RESULTS

The study included 71 NS (43 NS1 and 28 NS2) and 110 controls. With a threshold of ≥1.7, sensitivity and specificity of the specific AI test were 90.7% (CI 77.7 to 97.4) and 100% (CI 96.7 to 100.0), respectively, for NS1 and 14.3% (CI 4 to 32.7) and 100% (CI 96.7 to 100.0) for NS2. In patients suspected of NS with a CNS involvement (NS1 group), NS could be confirmed by the positivity of this specific AI.

CONCLUSIONS

Measurement of an intrathecal synthesis index of specific anti-T. pallidum IgG in patients with CSF inflammatory signs appears to be a valuable diagnostic test. However, in otic or ocular syphilis, presenting few CSF abnormalities, AI is not sufficient alone to confirm NS diagnosis.

TRIAL REGISTRATION

Swiss Association of Research Ethics Committees number 2019-00232.

Meningovascular Neurosyphilis with Cerebral Hemorrhaging in a Human Immunodeficiency Virus-1-positive Patient

Meningovascular neurosyphilis is a rare manifestation of early neurosyphilis that causes infectious arteritis and ischemic infarction. We herein report a 44-year-old man with meningovascular neurosyphilis who presented with cerebral hemorrhaging. He complained of nausea, vomiting and lightheadedness. The patient tested positive for human immunodeficiency virus (HIV), and head computed tomography showed cerebral hemorrhaging in the upper right frontal lobe and left subcortical parietal lobe. Positive cerebrospinal fluid syphilis tests confirmed the diagnosis. He recovered after treatment for neurosyphilis and anti-HIV therapy. Our case highlights the importance of considering meningovascular neurosyphilis in young patients with multiple instances of cerebral hemorrhaging.

Intrathecal Synthesis Index of Specific Anti-Treponema IgG: a New Tool for the Diagnosis of Neurosyphilis

Neurosyphilis (NS) diagnosis is challenging because clinical signs are diverse and unspecific, and a sensitive and specific laboratory test is lacking. We tested the performance of an antibody index (AI) for intrathecal synthesis of specific anti-Treponema IgG by enzyme-linked immunosorbent assay (ELISA) for NS diagnosis. We conducted a retroprospective monocentric study including adults with neurological symptoms who had serum and cerebral spinal fluid (CSF) samples collected between 2006 and 2021. Two NS definitions were used. NS1 included patients with neurological symptoms, positive Treponema pallidum particle agglutination (TPPA) serology, and CSF-TPPA of ≥320, as well as CSF-leukocytes of >5 cells/mm³ and/or CSF-protein of >0.45 g/L and/or a reactive CSF-VDRL/RPR test. NS2 included patients with acute ocular and/or otologic symptoms, positive TPPA serology, and a response to NS treatment. Controls were patients with central nervous system disorders other than neurosyphilis. Anti-Treponema pallidum IgG were measured simultaneously in serum and CSF, and AI was calculated according to Reiber diagram. We assessed the AI test area under the curve (AUC), sensitivity/specificity, and estimated positive and negative predictive values. In total, 16 NS1 patients, 11 NS2 patients, and 71 controls were included. With an AI of ≥1.7 as a positive test for NS diagnostic, specificity was 98.6% (95% confidence interval [CI 95%] of 92.4 to 100.0) and sensitivity was 81.3% (CI 95% of 54.4 to 96.0) for NS1 and 98.6% (CI 95% 92.4 to 100.0) and 27.3% (CI 95% 6.0 to 61.0), respectively, for NS2. Positive and negative predictive values were >95% for NS1 and >85% for NS2, for prevalence above and below 20%. Measuring an AI for intrathecal synthesis of specific anti-Treponema pallidum IgG is a new promising tool highly specific for NS diagnosis.

IMPORTANCE In the context of a lack of a gold standard for the diagnosis of neurosyphilis due to either nonspecific or nonsensitive tests, we present in this article a new promising tool highly specific for NS diagnosis. This new test involves measuring an intrathecal synthesis index of specific anti-Treponema IgG by ELISA.

Neurosyphilis masquerading as oculomotor nerve palsy in a healthy middle-aged man: Case report and review of the literature

Acquired isolated oculomotor nerve palsy (ONP) is a commonly encountered clinical entity in ophthalmology. While most cases are due to microvascular ischemia, the diagnosis of ONP requires careful evaluation for alternate life-threatening etiologies. We present a case of isolated complete pupil-involving ONP in a healthy 47-year-old man in whom aneurysmal compression was initially suspected. Investigations later revealed a diagnosis of neurosyphilis. Neurosyphilis is an extremely rare cause of isolated ONP and seldom reported in the literature. Timely recognition of this disease by ophthalmologists can help orient patients to the appropriate neurology and infectious disease services they need.

T2/FLAIR hyperintensity in the mesial temporal lobe: challenging differential diagnosis

T2/FLAIR hyperintensity in the mesial temporal lobe is the most common MR finding of herpes simplex encephalitis but may be observed in other infectious and non-infectious diseases. The former includes herpes human virus 6 encephalitis, Japanese encephalitis, and neurosyphilis, and the latter autoimmune encephalitis, gliomatosis cerebri, bilateral or paradoxical posterior cerebral artery infarction, status epilepticus, and hippocampal sclerosis. Thus, T2/FLAIR hyperintensity in the mesial temporal lobe is not a disease-specific magnetic resonance imaging finding, and these conditions must be differentiated to ensure proper treatment. We review diseases that are presented with T2/FLAIR hyperintensity in the mesial temporal lobe and provide a helpful flow chart based on clinical and radiologic features.

Neurologic Disorders of the Maxillofacial Region

The maxillofacial region is complex in its anatomy and in its variation in the presentation of neurologic disorders. The diagnosis and management of neurologic disorders in clinical practice remains a challenge. A good understanding of the neurologic disorder in its entirety helps dentists in the diagnosis and appropriate referral to a specialist for further investigations and management of the condition. Neurologic disorders described in this article are under broad categories of sensory and motor disturbances as well as movement disorders and infections. This article summarizes the most common maxillofacial neurologic disorders that dentists might encounter in clinical practice.

Antibiotic therapy for adults with neurosyphilis

BACKGROUND

Neurosyphilis is an infection of the central nervous system, caused by Treponema pallidum, a spirochete capable of infecting almost any organ or tissue in the body causing neurological complications due to the infection. This disease is a tertiary manifestation of syphilis. The first-line treatment for neurosyphilis is aqueous crystalline penicillin. However, in cases such as penicillin allergy, other regimes of antibiotic therapy can be used.

OBJECTIVES

To assess the clinical effectiveness and safety of antibiotic therapy for adults with neurosyphilis.

SEARCH METHODS

We searched the Cochrane Library, CENTRAL, MEDLINE, Embase, LILACS, World Health Organization International Clinical Trials Registry Platform and Opengrey up to April 2019. We also searched proceedings of eight congresses to a maximum of 10 years, and we contacted trial authors for additional information.

SELECTION CRITERIA

We included randomised clinical trials that included men and women, regardless of age, with definitive diagnoses of neurosyphilis, including HIV-seropositive patients. We compared any antibiotic regime (concentration, dose, frequency, duration), compared to any other antibiotic regime for the treatment for neurosyphilis in adults.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected eligible trials, extracted data, and evaluated risk of bias. We resolved disagreements by involving a third review author. For dichotomous data (serological cure, clinical cure, adverse events), we presented results as summary risk ratios (RR) with 95% confidence intervals (CI). We assessed the quality of evidence using the GRADE approach.

MAIN RESULTS

We identified one trial, with 36 participants​ diagnosed ​with syphilis and HIV. The participants were mainly men, with a median age of 34 years. This trial, ​funded by a pharmaceutical company, compared ceftriaxone in 18 participants (2 g daily for 10 days), with penicillin G, also in 18 participants (4 million/Units (MU)/intravenous (IV) every 4 hours for 10 days). The trial reported incomplete and inconclusive results. Three of 18 (16%) participants receiving ceftriaxone versus 2 of 18 (11%) receiving penicillin G achieved serological cure (RR 1.50; 95% CI: 0.28 to 7.93; 1 trial, 36 participants very low-quality evidence); and 8 of 18 (44%) participants receiving ceftriaxone versus 2 of 18 (18%) participants receiving penicillin G achieved clinical cure (RR 4.00; 95% CI: 0.98 to 16.30; 1 trial, 36 participants very low-quality evidence). Although more participants who received ceftriaxone achieved serological and clinical cure compared to those who received penicillin G, the evidence from this trial was insufficient to determine whether there was a difference between treatment with ceftriaxone or penicillin G.In this trial, the authors reported what would usually be adverse events as symptoms and signs in the follow-up of participants. Furthermore, this trial did not evaluate recurrence of neurosyphilis, time to recovery nor quality of life. We judged risk of bias in this clinical trial to be unclear for random sequence generation, allocation, ​and blinding of participants, and high for incomplete outcome data, potential conflicts of interest (funding bias), and other bias, due to the lack of a sample size calculation. We rated the quality of evidence as very low.

AUTHORS' CONCLUSIONS

Due to low quality and insufficient evidence, it was not possible to determine whether there was a difference between treatment with ceftriaxone or Penicillin G. Also, the benefits to people without HIV and neurosyphilis are unknown, as is the ceftriaxone safety profile.Therefore, these results should be interpreted with caution. This conclusion does not mean that antibiotics should not be used for treating this clinical entity. This Cochrane Review has identified the need of adequately powered trials, which should be planned according to Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) recommendations, conducted and reported as recommended by the CONSORT statement. Furthermore, the outcomes should be based on patients' perspectives taking into account Patient-Centered Outcomes Research Institute (PCORI) recommendations.

Medullary involvement in neurosyphilis: a report of 12 cases and a review of the literature

Study design

Retrospective case series.

Objectives

To describe the epidemiological, clinical, MRI and therapeutic features and the outcomes of patients with syphilitic myelitis in a third-level hospital in Marrakesh in southern Morocco.

Setting

The Neurology Department, University Hospital Mohamed VI Marrakesh, Morocco.

Methods

Twelve charts of persons with syphilitic myelitis over a period of 17 years were reviewed to determine demographics, presenting symptoms, clinical and radiological findings, biological features, treatment received and outcomes.

Results

There were 120 reports of neurosyphilis. Twelve patients (10%) had syphilitic myelitis. Eleven patients (92%) were male with mean age of 44 at presentation. Tabes dorsalis was the most common clinical form. Cerebrospinal fluid analysis showed lymphocytic meningitis in nine patients (75%). Spine MRI was abnormal in four patients (33%). All patients were treated with 30 million units of aqueous penicillin G IV per day for 10 days, every 3 months. In follow-up, two patients (17%) with clinical syphilitic meningomyelitis improved significantly, eight patients (66%) with tabes dorsalis and subacute transverse myelitis showed partial improvement but clinical status was stationary for two patients (17%) with Erb paraplegia.

Conclusions

All patients with myelopathy should undergo syphilitic serology because of nonspecific manifestations and curability of this disease.

Cerebral Syphilitic Gumma Can Arise Within Months of Reinfection: A Case of Histologically Proven Treponema pallidum Strain Type 14b/f Infection With Human Immunodeficiency Virus Positivity

A 44-year-old man with human immunodeficiency virus positivity developed cerebral gumma 6 months after appropriate therapy for secondary syphilis. It was surgically resected and histologically, Treponema pallidum (14b/f, a relatively rare strain type) was proven. A complete set of modern techniques was performed to depict rare complication of this classic disease.

Oral ulcers as a presentation of secondary syphilis

The incidence of syphilis is increasing, and it typically presents in patients with known risk factors, often to genitourinary physicians. Patients presenting to a dermatologist or ophthalmologist will more likely have secondary syphilis, with the potential for having the associated complications. Early recognition is therefore vital to limit both the disease and risk of further contact spread. In this review, we include two case histories demonstrating the value of recognizing oral signs. Additionally, we review the currently accepted diagnostic and therapeutic recommendations.

Neurosyphilis as a Cause of Transverse Myelitis in a Teenage Girl

BACKGROUND

Syphilis is a sexually transmitted infection that was nearly eradicated in 2001 but is now making a resurgence. It has a wide range of clinical manifestations depending on disease stage. Neurosyphilis is an infrequently seen infectious disease with central nervous system involvement that can occur in either early- or late-stage syphilis. The diagnosis of neurosyphilis is challenging, primarily because Treponema pallidum, the infecting organism, cannot be cultured in vitro. This article describes a patient with neurosyphilis and reviews the epidemiology and clinical manifestations, diagnostics, and treatment of neurosyphilis.

CASE REPORT

In compliance with the request of the Privacy Board of our institution, the numerical age of this patient has been omitted. A sexually active teenage girl who was treated for primary syphilis 2 years earlier presented to a tertiary children's hospital with paresthesia and weakness of her right leg, left arm, and neck. Magnetic resonance imaging revealed cervical intramedullary cord edema consistent with transverse myelitis. Serum studies showed positive syphilis enzyme immunoassay, T. pallidum particle agglutination assay, and fluorescent treponemal antibody absorption. A serum rapid plasma reagin test was negative. A lumbar puncture was performed with normal cell count and protein. A cerebrospinal fluid Venereal Disease Research Laboratory test was negative. She was diagnosed with neurosyphilis and treated with intravenous steroids and penicillin G, with near complete resolution of symptoms. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: The Centers for Disease Control and prevention has noted a steady rise of the incidence of syphilis since 2002. Emergency physicians should be familiar with the spectrum of the clinical manifestations of syphilis, challenges in diagnostics, and appropriate treatment course.

Neurosyphilis as a great imitator: a case report

Background

Neurosyphilis is defined as any involvement of the central nervous system by the bacterium Treponema pallidum. Movement disorders as manifestations of syphilis have been reported quite rarely.

Case presentation

We report a case of a 42-year-old Russian man living in Estonia with rapidly progressive dementia and movement disorders manifesting as myoclonus, cerebellar ataxia and parkinsonism. The mini mental state examination score was 12/30. After excluding different neurodegenerative causes, further diagnostic testing was consistent with neurosyphilis. Treatment with penicillin was started and 6 months later his mini mental state examination score was 25/30 and he had no myoclonus, parkinsonism or cerebellar dysfunction.

Conclusion

Since syphilis is easily diagnosed and treatable, it should be considered and tested in patients with cognitive impairment and movement disorders.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-016-2176-2) contains supplementary material, which is available to authorized users.

Psychosis or Simply a New Manifestation of Neurosyphilis?

The widespread use of antibiotics in recent years has caused a significant reduction in the incidence of neurosyphilis and changes in its clinical features. We present a case that initially presented as persistent headache and untreatable psychosis. Neurosyphilis was diagnosed during the clinical evaluation. Blood serum analyses for syphilis were positive for rapid plasma reagin titres, the Venereal Disease Research Laboratories test and fluorescent treponemal antibody absorption. A lumbar puncture was performed and cerebrospinal fluid analysis resulted in the diagnosis of neurosyphilis. The patient completed a 2-week course of treatment with aqueous crystalline penicillin G and his symptoms subsequently improved. We suggest that neurosyphilis should always be included in the differential diagnosis of untreatable psychosis.

Canadian Public Health Laboratory Network laboratory guidelines for the diagnosis of neurosyphilis in Canada

Neurosyphilis refers to infection of the central nervous system by Treponema pallidum, which may occur at any stage. Neurosyphilis has been categorized in many ways including early and late, asymptomatic versus symptomatic and infectious versus non-infectious. Late neurosyphilis primarily affects the central nervous system parenchyma, and occurs beyond early latent syphilis, years to decades after the initial infection. Associated clinical syndromes include general paresis, tabes dorsalis, vision loss, hearing loss and psychiatric manifestations. Unique algorithms are recommended for HIV-infected and HIV-uninfected patients, as immunocompromised patients may present with serologic and cerebrospinal fluid findings that are different from immunocompetent hosts. Antibody assays include a VDRL assay and the FTA-Abs, while polymerase chain reaction for T. pallidum can be used as direct detection assays for some specimens. This chapter reviews guidelines for specimen types and sample collection, and identifies two possible algorithms for use with immunocompromised and immunocompetent hosts using currently available tests in Canada, along with a review of treatment response and laboratory testing follow-up.

Recent trends in the serologic diagnosis of syphilis

Complexities in the diagnosis of syphilis continue to challenge clinicians. While direct tests (e.g., microscopy or PCR) are helpful in early syphilis, the mainstay of diagnosis remains serologic tests. The traditional algorithm using a nontreponemal test (NTT) followed by a treponemal test (TT) remains the standard in many parts of the world. More recently, the ability to automate the TT has led to the increasingly widespread use of reverse algorithms using treponemal enzyme immunoassays (EIAs). Rapid, point-of-care TTs are in widespread use in developing countries because of low cost, ease of use, and reasonable performance. However, none of the current diagnostic algorithms are able to distinguish current from previously treated infections. In addition, the reversal of traditional syphilis algorithms has led to uncertainty in the clinical management of patients. The interpretation of syphilis tests is further complicated by the lack of a reliable gold standard for syphilis diagnostics, and the newer tests can result in false-positive reactions similar to those seen with older tests. Little progress has been made in the area of serologic diagnostics for congenital syphilis, which requires assessment of maternal treatment and serologic response as well as clinical and laboratory investigation of the neonate for appropriate management. The diagnosis of neurosyphilis continues to require the collection of cerebrospinal fluid for a combination of NTT and TT, and, while newer treponemal EIAs look promising, more studies are needed to confirm their utility. This article reviews current tests and discusses current controversies in syphilis diagnosis, with a focus on serologic tests.

Impact of HIV-1 infection on the clinical presentation of syphilis in men who have sex with men

Men who have sex with men (MSM), especially those with HIV-1 infection, are disproportionately affected by syphilis in higher income countries. The course, and some of the clinical features of the disease, especially the development of neurosyphilis, can be affected by HIV-1 co-infection. This review documents potential differences in the clinical features of syphilis in HIV-1 infected and uninfected MSM and highlights the importance of a thorough examination and high index of suspicion when seeing and treating MSM at risk of sexually transmissible infections.

Stroke after Initiating IV Penicillin for Neurosyphilis: A Possible Jarisch-Herxheimer Reaction

Introduction. Syphilis incidence has increased in the US in the last decade. Jarisch-Herxheimer reaction (JHR) is a well-documented adverse effect of penicillin treatment in syphilis. Stroke has not been reported as part of its phenomenology. Case Report. A 57-year-old man presented with worsening memory. His minimental status examination score was 14/30. Serum RPR test was positive and VDRL test in the CSF was reactive. Within six hours of first dose of IV crystalline penicillin G, he was found to have hemineglect and difficulty moving the left leg. MRI of the brain showed multiple acute ischemic strokes. Immediate MRA ruled out vascular occlusion. Penicillin treatment was stopped. Four hours later, he was found to be febrile and had two episodes of generalized tonic-clonic seizures. Conclusions. We report a case of confirmed neurosyphilis with no known modifiable stroke risk factors, who developed acute ischemic stroke and other constitutional symptoms consistent with JHR after IV penicillin. This is the first reported case in literature where an acute ischemic stroke can be attributed to Jarisch-Herxheimer reaction. Given an increase in incidence of syphilis in recent years, our case underlies the importance of keeping in mind potential catastrophic drug adverse reactions in neurosyphilis patients.

Toxoplasma gondii infection, from predation to schizophrenia: can animal behaviour help us understand human behaviour?

We examine the role of the protozoan Toxoplasma gondii as a manipulatory parasite and question what role study of infections in its natural intermediate rodent hosts and other secondary hosts, including humans, may elucidate in terms of the epidemiology, evolution and clinical applications of infection. In particular, we focus on the potential association between T. gondii and schizophrenia. We introduce the novel term 'T. gondii-rat manipulation-schizophrenia model' and propose how future behavioural research on this model should be performed from a biological, clinical and ethically appropriate perspective.

The role of parasites and pathogens in influencing generalised anxiety and predation-related fear in the mammalian central nervous system

Behavioural and neurophysiological traits and responses associated with anxiety and predation-related fear have been well documented in rodent models. Certain parasites and pathogens which rely on predation for transmission appear able to manipulate these, often innate, traits to increase the likelihood of their life-cycle being completed. This can occur through a range of mechanisms, such as alteration of hormonal and neurotransmitter communication and/or direct interference with the neurons and brain regions that mediate behavioural expression. Whilst some post-infection behavioural changes may reflect 'general sickness' or a pathological by-product of infection, others may have a specific adaptive advantage to the parasite and be indicative of active manipulation of host behaviour. Here we review the key mechanisms by which anxiety and predation-related fears are controlled in mammals, before exploring evidence for how some infectious agents may manipulate these mechanisms. The protozoan Toxoplasma gondii, the causative agent of toxoplasmosis, is focused on as a prime example. Selective pressures appear to have allowed this parasite to evolve strategies to alter the behaviour in its natural intermediate rodent host. Latent infection has also been associated with a range of altered behavioural profiles, from subtle to severe, in other secondary host species including humans. In addition to enhancing our knowledge of the evolution of parasite manipulation in general, to further our understanding of how and when these potential changes to human host behaviour occur, and how we may prevent or manage them, it is imperative to elucidate the associated mechanisms involved.

Treatment of neurosyphilis

In 2001, the incidence of primary and secondary syphilis increased in the United States for the first time in a decade. Increasing rates of early syphilis among men who have sex with men have been reported in many American cities, with similar outbreaks noted in Canada and Europe. In San Francisco, the increase has been particularly sharp and accompanied by an increase in the incidence of neurosyphilis. Early neurosyphilis develops within weeks to years of primary infection and primarily involves the meninges. Syndromes include syphilitic meningitis (often accompanied by cranial neuropathies), meningovascular syphilis (with associated ischemic stroke), or asymptomatic neurosyphilis. Late neurosyphilis occurs years to decades after exposure as cerebral or spinal gummatous disease or the classic parenchymal forms affecting the brain (general paresis or syphilitic encephalitis) or spinal cord and nerve roots (tabes dorsalis). Treponema pallidum, the causative agent, cannot be cultured in vitro, and microscopic techniques are laborious. Thus, diagnosis depends on serologic tests and cerebrospinal fluid (CSF) examination. The suboptimal sensitivity and specificity of these tests complicate diagnosis, particularly among patients coinfected with HIV. CSF examination should be performed to evaluate for neurosyphilis in all patients with positive serum syphilis serology and neurologic, ophthalmic, or tertiary disease, or in those who have failed therapy, and in HIV-infected patients with late latent syphilis or syphilis of unknown duration. Intravenous penicillin G is the recommended treatment for all forms of neurosyphilis and for syphilitic eye disease. An outpatient alternative, if adherence can be assured, is intramuscular benzathine penicillin with oral probenecid. Newer drugs that penetrate CSF, such as ceftriaxone or azithromycin, have not yet been adequately tested for neurosyphilis. Syphilis facilitates transmission of HIV (and vice versa), and thus all patients diagnosed with syphilis should be offered HIV testing.