Use of PCR to diagnose Toxoplasma gondii chorioretinitis in eyes with severe vitritis

Polymerase chain reaction test for diagnosis of infectious uveitis

BACKGROUND

To study the clinical utility of broad-range real-time Polymerase Chain Reaction (PCR) assay in patients suspected for infectious uveitis and to analyze the clinical relevance.

METHODS

Medical records of patients with uveitis were assessed in whom PCR analysis of intraocular fluids was performed between January 2018 and February 2021. Intraocular samples were investigated for cytomegalovirus (CMV), Epstein-Barr virus (EBV), varicella zoster virus (VZV), herpes simplex viruses type 1 and 2 (HSV_1,2), human T-lymphotropic virus type 1 (HTLV-1), Toxoplasma gondii and also for bacterial 16 S and fungal 18 S/28S ribosomal DNA (rDNA).

RESULTS

Aqueous paracentesis and vitreous sampling was done for 151 (81.2%) and 35 (18.8%) patients, respectively. Most of the patients had panuveitis (61.3%). PCR results were positive in 69 out of 186 patients (37%) according to the following order: CMV (18 cases), VZV (18 cases), fungal 18s/28s rDNA (17 cases), HSV (9 cases), bacterial 16s rDNA (3 cases), HTLV-1 (2 cases), and Toxoplasma gondii (2 cases). PCR positivity rate was 5.8% in patients with undifferentiated panuveitis. EBV was not detected at all. Initial treatment was changed in 38 patients (20%) based on PCR results. The overall sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of PCR test for aqueous samples was 82%, 91%, 96%, and 87%, respectively. No significant adverse effect related to sampling was reported.

CONCLUSION

PCR analysis of intraocular fluids in patients with suspected infectious uveitis plays an important role in confirming diagnosis or changing treatment with good predictive value. However, routine PCR test in patients with undifferentiated panuveitis in order to rule out possible underlying infectious etiology had low benefit.

Differential Diagnosis of Vitritis in Adult Patients

The term "vitritis" refers to the presence of a cellular infiltration of the vitreous body, usually in the context of an intraocular inflammation, but not exclusively. Intermediate uveitis is the most prominent cause of vitritis, including infectious and auto-immune/auto-inflammatory etiologies. Corticosteroids and immunosuppressive therapies should not be started before ruling out the infectious causes of vitritis, especially in immunosuppressed individuals. Other situations can mimic intermediate uveitis such as amyloidosis and ocular tumors. Primary intraocular lymphoma should always be suspected in case of vitreous infiltrations in individuals aged over 50 years.

Role of molecular diagnostics in ocular microbiology

Although microbial culture remains the gold standard for diagnosis of many ocular infections, the technique is limited by low yield, inability to detect certain organisms, and potentially long delays to results. DNA-based molecular diagnostic techniques use detection of specific nucleic acid sequences as evidence for presence of suspected pathogens. The polymerase chain reaction (PCR) is a powerful molecular biology technique that allows for detection of fewer than 10 copies of pathogen genome. Recent technical advances in PCR have permitted quantitation of pathogen load using quantitative PCR (qPCR), and have permitted multiplexing of primer sets. Use of pan-bacterial and pan-fungal primers for ribosomal DNA sequences has allowed diagnosis of bacterial and fungal infections using molecular techniques. In this review, we highlight recent advances in the application of PCR to the diagnosis of anterior segment and posterior segment ocular infectious diseases.

Real-time polymerase chain reaction and intraocular antibody production for the diagnosis of viral versus toxoplasmic infectious posterior uveitis

PURPOSE

The aim of this work was to determine the diagnostic performance of real-time polymerase chain reaction (RT-PCR) and to assess intraocular specific antibody secretion (Goldmann-Witmer coefficient) on samples from patients with signs of posterior uveitis presumably of infectious origin and to target the use of these two biologic tests in the diagnostic of Toxoplasma/viral Herpesviridae posterior uveitis by the consideration of clinical behavior and delay of intraocular sampling.

METHODS

Aqueous humour and/or vitreous fluid were collected from patients suspected of having posterior uveitis of infectious origin at presentation (140 samples). The diagnosis was confirmed by quantification of antibodies with the Goldmann-Witmer coefficient (GWC) and for detection of Herpesviridae and Toxoplasma gondii genomes with RT-PCR. Forty-one patients had final diagnosis of uveitis of non-Toxoplasma/non-viral origin and 35 among them constituted the control group. The main outcome measures were sensitivity, specificity, and positive and negative predictive values (PPV and NPV).

RESULTS

When pre-intraocular testing indication was compared with final diagnosis, GWC was a more sensitive and specific method than RT-PCR, and was successful in detecting T. gondii, especially if the patient is immunocompetent and the testing is carried out later in the disease course, up to 15 months. For viral Herpesviridae uveitis, the sensitivity and PPV of PCR evaluation was higher than detected with GWC with respectively 46% compared with 20% for sensitivity and 85% versus 60% for PPV. In either viral retinitis or toxoplasmosis infection, RT-PCR results were positive from 24 h, although GWC was not significant until 1 week after the onset of signs. In toxoplasmosis patients, positive RT-PCR results were statistically correlated with the chorioretinitis area (more than three disc areas; p = 0.002), with the age older than 50 (p = 0.0034) and with a clinical anterior inflammation (Tyndall ≥1/2+) and panuveitis; (p = 0.0001).

CONCLUSIONS

For the diagnosis of viral or toxoplasmosis-associated intraocular inflammation, the usefulness of laboratory diagnosis tools (RT-PCR and GWC) depends on parameters other than the sensitivity of the tests. Certain patient characteristics such as the age of the patients, immune status, duration since the onset of symptoms, retinitis area, predominant site and extent of inflammation within the eye should orientate the rational for the choice of laboratory testing in analysis of intraocular fluids.

A 13-year retrospective review of polymerase chain reaction testing for infectious agents from ocular samples

PURPOSE

Polymerase chain reaction (PCR) is a molecular technique for the diagnosis of ocular infectious disease. In this large patient sample and multiyear study, the impact of PCR for detecting infectious agents from ocular samples was reviewed in comparison with nonmolecular diagnostic techniques.

DESIGN

A retrospective laboratory review of PCR testing.

PARTICIPANTS

Three thousand fifty-six patient samples with a differential of ocular infection.

METHODS

The daily laboratory logs for diagnostic testing were reviewed for PCR, cell culture isolation, shell vial isolation, and Acanthamoeba isolation from January 1997 through May 2010 for herpes simplex virus (HSV), adenovirus, varicella zoster virus (VZV), Chlamydia trachomatis, Acanthamoeba, and infrequent pathogens of intraocular inflammation.

MAIN OUTCOME MEASURES

Incidence of the positive presence of ocular infectious agents.

RESULTS

Polymerase chain reaction results were positive more often than culture results for HSV (P = 0.0001), VZV (P = 0.00001), C. trachomatis (P = 0.00005), and Acanthamoeba (P = 0.04). For adenovirus, cell culture isolation results were positive more often than PCR results (P = 0.001). Polymerase chain reaction was the primary diagnostic test for detecting cytomegalovirus and Toxoplasma.

CONCLUSIONS

The current study demonstrated the importance of PCR as a routine diagnostic test for detecting both common and infrequent ocular pathogens. Cell culture isolation is still a definitive test for adenovirus and a confirmatory test for HSV and Acanthamoeba.

A prospective study of diagnosis of Toxoplasma gondii infection after bone marrow transplantation

Active infection with Toxoplasma gondii in immunocompromised transplant recipients can lead to toxoplasmosis, which may have a rapid disease course and in some cases be fatal. It is of paramount importance to diagnose toxoplasmosis at an early stage, and to initiate specific treatment to improve the outcome. Polymerase chain reaction (PCR) is today the primary diagnostic tool to diagnose toxoplasmosis in immunocompromised patients. Timely diagnosis may, however, be difficult if toxoplasmosis is at first asymptomatic. To investigate the magnitude of toxoplasmosis after bone marrow transplantation (BMT), we conducted a screening study by PCR where 21 autologous and 12 allogeneic BMT recipients were included. Peripheral blood samples were taken one week prior to BMT; thereafter, blood samples were drawn weekly for the first 6 months, and monthly up to one year after BMT. The samples were analyzed by conventional PCR and real-time PCR. T. gondii DNA was detected in peripheral blood from one patient 5 days post allogeneic BMT. There were no clinical signs of toxoplasmosis. Medical records were reviewed and showed a previously undiagnosed eye infection in another allogeneic BMT recipient. These two patients were seropositive for T. gondii. We concluded that monitoring for T. gondii DNA in peripheral blood samples using PCR might be a valuable method for identifying toxoplasma-seropositive stem cell transplant recipients.

Comparison of immunoblotting, calculation of the Goldmann-Witmer coefficient, and real-time PCR using aqueous humor samples for diagnosis of ocular toxoplasmosis

We compared three biological methods for the diagnosis of ocular toxoplasmosis (OT). Paired aqueous humor and serum samples from 34 patients with OT and from 76 patients with other ocular disorders were analyzed by three methods: immunoblotting or Western blotting (WB), the calculation of the Goldmann-Witmer coefficient (GWC), and PCR. WB and GWC each revealed the intraocular production of specific anti-Toxoplasma immunoglobulin G in 81% of samples (30 of 37). PCR detected toxoplasmic DNA in 38% of samples (13 of 34). Nine of the 13 PCR-positive patients were immunocompetent. Combining the techniques significantly improved the diagnostic sensitivity, to 92% for the GWC-WB combination, 90% for the WB-PCR combination, and 93% for the GWC-PCR combination. The combination of all three techniques improved the sensitivity to 97%.

Correlation between clinical suspicion and polymerase chain reaction verification of infectious vitritis

PURPOSE

To compare polymerase chain reaction (PCR) results to presumptive clinical diagnosis in patients with vitritis.

DESIGN

Retrospective review of PCR laboratory records from vitreous samples.

METHODS

Fifty consecutive laboratory records of vitreous samples sent for PCR testing were reviewed. Three reviewers with uveitis training ranked the clinical suspicion of a specific diagnosis using a classification system (scale of 1 to 4) and were masked to the PCR results.

RESULTS

The degree of clinical suspicion of a particular diagnosis was significantly associated with a positive PCR result (P = .048). Higher clinical suspicion was significantly more associated with a positive PCR result compared with cases with lower clinical suspicion (P = .01).

CONCLUSIONS

If the clinical suspicion of a specific diagnosis is low, the PCR for any infectious etiology is unlikely to be positive.

Polymerase chain reaction and Goldmann-Witmer coefficient analysis are complimentary for the diagnosis of infectious uveitis

PURPOSE

To determine the relative contribution of the analysis of intraocular antibody production and the polymerase chain reaction (PCR) in aqueous humor (AH) to the diagnosis of infectious uveitis.

DESIGN

Retrospective case-control study.

METHODS

Paired AH and serum samples from 230 patients suspected of infectious uveitis were examined for intraocular antibody production against herpes simplex virus (HSV), varicella zoster virus (VZV), and Toxoplasma gondii by calculating the Goldmann-Witmer coefficient (GWC). In addition, AH samples were investigated by real-time PCR to determine the presence of microbial DNA.

RESULTS

Positive results were obtained in 54 cases (23%): 13 HSV (24%), 16 VZV (30%), and 25 T gondii (46%). Of these, 23 (43%) were positive for both GWC and PCR, 26 (48%) only for GWC, and 5 (9%) only for PCR. With PCR as the sole diagnostic approach, a correct diagnosis of the infectious etiology would have been missed in 34% of cases for the herpes viruses and in 64% for T gondii. Analysis of the relationship between a positive laboratory diagnosis and the time of sampling after onset of ocular disease demonstrated that intraocular antibody production was found throughout the course of the diseases. Viral DNA was more readily detected early in infection. In contrast, T gondii nucleic acid was not detected until 3 weeks after onset of ocular disease.

CONCLUSIONS

Analysis of intraocular antibody production contributed considerably to the etiological diagnosis of infectious uveitis, most notably of ocular toxoplasmosis early after onset of disease. Therefore, both PCR and GWC determination might be performed for comprehensive diagnosis of intraocular infections.