Preeclampsia (PE) complicates 2–5 % of all pregnancies worldwide [1] and is a heterogeneous multiorgan disorder characterized by variable degrees of placental malperfusion [2]. PE is a major cause of maternal and perinatal morbidity and mortality [2] and can present with a wide variety of symptoms [[3], [4]]. The only definitive treatment for PE is delivery of the placenta [5].

Research has been focusing on distinguishing women who are likely to develop or with established PE from those who do not amongst those presenting with symptoms of the disorder in order to plan subsequent monitoring and timed delivery. The angiogenic markers sFlt-1 (soluble fms-like tyrosine kinase 1) and PlGF (placenta growth factor) are associated with placental dysfunction and the sFlt-1/PlGF ratio is elevated in patients with a confirmed diagnosis of PE [6]. Two landmark studies, PROGNOSIS and PROGNOSIS ASIA, have demonstrated that Elecsys sFlt-1/PlGF ratio could be used to rule-in (cut off ≥ 38) or rule-out (<38) preterm PE within 7 days or 4 weeks of assessment respectively [[7], [8]]. Alternatively, the level of PlGF determined by either DELFIA Xpress PlGF-1–2-3 (<50 pg/mL) (PerkinElmer Wallac Oy, Turku, Finland) or Quidel Triage PlGF Tests (<99 pg/mL) (Quidel Corporation, San Diego, USA) can also be used to rule-in preterm PE. Equally, the Triage PlGF Test (≥100 pg/mL) and PlGF-1–2-3 tests (≥150 pg/mL) can also rule-out PE within 2 or 4 weeks of assessment [[9], [10]].

The Elecsys sFlt-1/PlGF ratio and DELFIA Xpress PlGF-1–2-3 tests require dedicated immunoanalyzers in laboratories for the measurement of serum proteins extracted from maternal blood samples. The Triage PlGF test, whilst potentially a point-of-care test (PoC), still requires the separation of serum from whole blood before PlGF levels can be deteremined. The cost of the reagents and the need for technical staff make current assessed tests expensive, particularly in low and middle income countries where the incidence of PE is at its highest. The National Institute for Health and Care Excellence (NICE) from the United Kingdom has estimated economic cost per test for the Triage PlGF, DELFIA Xpress PlGF-1–2-3 and Elecsys sFlt-1/PlGF ratio as ≈£50, ≈£37 and ≈£79, respectively.

The urine congophilia-based paper test, ‘Congo Red dot test (CRDT)’, is based on the premise that abnormal amyloid proteins excreted in the urine of patients with PE would bind to the Congo red dye resulting in the phenomenon referred to as urine congophilia and the degree of dispersion can be assessed as “negative” or “positive” according to the dye spread pattern from a central area [11]. Urine congophilia has therefore been proposed as a PoC test for triaging symptomatic patients and alternatively as a routine screening test in asymptomatic patients for the prediction and rapid identification of PE as the excreted proteins in urine of patients who develop PE have been reported to be detectable well before the onset of clinical symptoms [[12], [13], [14]]. It has been proposed as a simple inexpensive yes/no test to rule-in or rule-out PE within minutes requiring no technical expertise which can be used by any healthcare providers at the point of care [[12], [13]]. Early studies assessing the urine CRDT performance in patients presenting with suspected PE reported both high sensitivity and specificity [[12], [13], [15]]. These studies however may be confounded as they appeared to have included patients with established PE at the time of CRDT testing or CRDT testing was performed under research conditions by trained technicians. At present there is little to no data to determine if the urine CRDT would have similar clinical utility as reported in initial studies. The aims of the current study were to evaluate the diagnostic performance and clinical utility of the urine CRDT test in a cohort of East Asian pregnant patients presented with clinical features of PE prior to performing the CRDT and assess the CRDT test result relative to the time of development of PE.