Population

Almost all adults

Setting

Mostly university hospitals, employing exclusively 1.5T or 3T MRI scanners

Index test

Dynamic susceptibility contrast MR perfusion (commonly gradient echo rather than spin echo sequence acquisition), usually without contrast preload, typically using arterial input function or gamma variate function post‐processing algorithms, and preferentially using region‐of‐interest method to obtain Max rCBV values (CBV ratio of tumour: contralateral normal appearing white matter)

Importance

For solid and non‐enhancing brain tumours with low rCBV, patients with no or little neurologic deficit may opt for conservative management over surgery to avoid early neurologic disability. Meanwhile, patients with high rCBV could favour early treatment for better tumour control.

Reference standard

All with histologic examinations, majority with resection.

Studies

Mostly prospective cross sectional studies (no case‐control studies)

Positive Test

Summary accuracy
(95% CI) using bivariate model

No. of study participants / selected patients
(No. of studies)

Prevalence

Implications

Quality of studies
(Based on QUADAS‐2 applied on study design and selected patients)

Comments

rCBV threshold <1.75 indicates LGG

Sensitivity

(proportion of LGG detected by MR perfusion)

0.83

(0.66, 0.93)

Specificity

(proportion of HGG detected by MR perfusion)

0.48

(0.09 to 0.90)

392 patients /

115 with solid non‐enhancing Grade II‐IV gliomas who underwent tissue sampling within 2 months of MR perfusion

(7 studies)

In a hypothetical population of solid and non‐enhancing Grade II‐IV gliomas, the prevalence of LGGs and HGGs is 72% and 28%, respectively.

Given 100 patients with solid and non‐enhancing infiltrative gliomas, 72 will have LGG and 28 with HGG.

Of 72 patients with LGG, it is expected 12 patients will be misclassified to have HGG (but this could potentially be between 5 to 24 patients) and may undergo surgery, thus risking early neurologic deterioration. Meanwhile, of 28 patients with HGG, 15 will be misclassified to have LGG (but this could be between 3 to 25 patients), which may lead to a delay in treatment that can potentially adversely affect outcomes.

Generally low risk of bias in the patient selection domain, excepting 2 out of 7 studies with unclear patient sampling and inappropriate exclusion of small tumours.

High risk of bias in the index test domain, mainly because 6 out of 7 studies did not use a pre‐specified threshold. However this did not affect meta‐analysis as we used a common rCBV threshold of 1.75.
Generally low risk of bias in the reference standard domain, excepting 2 out of 7 studies with unclear method of histologic confirmation and/or presence of blinding.
Low risk of bias in the flow and timing domain.

Low concerns of applicability for the patient selection, index test and reference standard domains by using patient‐level data.

Low numbers (4 to 48) with target and alternative conditions per study and only 2 studies had >20 patients.

In general, individual studies had heterogeneous sensitivity and specificity, both with wide confidence intervals.

Only 1 study had low risk of bias and low concern of applicability across all domains.

Five studies were considered good quality (i.e., with low risk of bias in the domains of reference standard and flow & timing). Their sensitivity analysis yielded sensitivity 0.80 (95% CI 0.61 to 0.91) and specificity 0.67 (95% CI 0.07 to 0.98).

Subgroup analysis showed sensitivity/specificity of [0.92 (95% CI 0.55 to 0.99)/ 0.42 (95% CI 0.02 to 0.95) in astrocytomas and 0.77 (95% CI 0.46 to 0.93)/0.53 (95% CI 0.14 to 0.88) in oligodendrogliomas + oligoastrocytomas.

Data were too sparse to investigate any differences across subgroups.