Photo-based External Quality Assessment of Malaria rapid diagnostic tests in a non-endemic setting

Abstract

IntroductionIn non-endemic settings, expertise in malaria microscopy is limited and rapid diagnostic tests (RDTs) are an adjunct to malaria diagnosis.AimWe performed an External Quality Assessment (EQA) on reading and interpretation of malaria RDTs in a non-endemic setting.MethodsParticipants were medical laboratories in Belgium and the Grand Duchy of Luxembourg using malaria RDTs; they received (i) 10 high-resolution photographs presenting test line combinations of RDTs with interpretations listed in a multiple choice format and (ii) a questionnaire about their practices of malaria diagnosis.ResultsAmong 135 subscribing laboratories, 134 (99.3%) used 139 RDT products (11 different products from 8 brands). After exclusion of the results of one laboratory, analysis was done for 133 laboratories using 137 RDT products. Scores of 10/10, 9/10 and 8/10 were achieved for 58.4%, 13.1% and 8.0% of 137 RDT products respectively. For three-band P. falciparum–pan-Plasmodium RDTs (113 (82.5%) products, 6 brands), most frequent errors were (1) disregarding faint test lines (18.6%), (2) reporting invalid instead of P. falciparum (16.8%) and (3) reporting “Plasmodium spp., no further differentiation possible” without mentioning the presence or absence of P. falciparum (11.5%). For four-band RDTs (21 (15.3%) products, 1 brand), errors were (4) disregarding faint P. vivax test lines (47.6%) and (5) reporting “Plasmodium spp., no further differentiation possible” without mentioning the presence of P. falciparum and P. vivax (28.6%). Instructions for use (IFU) of only 4 out of 10 RDT products mentioned to interpret faint-intensity test lines as positive (conducive to errors 1 and 4) and IFU of 2 products displayed incorrect information (conducive to errors 2 and 5). Outside of office hours, 36.1% of participants relied on RDTs as the initial diagnostic test; 13.9% did not perform microscopic confirmation.ConclusionReading and interpretation of malaria RDTs was satisfactory, but errors were embedded in the instructions for use of the products. Relying on RDTs alone for malaria diagnosis (about one third of participants) is not a recommended practice.

Adequacy of serial self-performed SARS-CoV-2 rapid antigen-detection testing for longitudinal mass screening in the workplace

“…13 In studies of malaria RADT, weak positive test bands consistently correlate with lower sensitivity. [11][12][13] Our study confirms these findings for SARS-CoV-2 RADT, and provides evidence for a simple and effective corrective intervention.…”

“…In this prospective field evaluation of self-performed SARS-CoV-2 RADT in an intended-use setting, the accuracy of signal interpretation was proportional to test band intensity, and was extremely low for tests with weak bands. An evidence-based Modified Quick Reference Guide improved signal interpretation by untrained workers to a level of accuracy comparable to that of professional technologists for other RADTs, 11,12 but did not have a major impact on the proper execution of procedural steps. Repeated self-testing was associated with improved signal interpretation, though the effect was less apparent with tailored instructions as initial accuracy was already high.…”

Loop-mediated isothermal amplification (LAMP) assay for the diagnosis of imported malaria: a narrative review

“…However, malaria microscopy is a labour intensive method whose quality strongly relies on well experienced personal, and in countries where relatively few cases of malaria are seen it may be difficult to maintain required levels of training also considering of the large number of laboratory staff who alternate in emergency services. Some studies have shown that prompt laboratory malaria diagnosis may be particularly challenging during outof-office hours when competent microscopists may not be available [8][9][10]. In a study conducted in Portugal half of all malaria smears were performed out-of hours (i.e., other than 9-17 Monday to Friday) but accounted for 61% of malaria diagnosis [11].…”

“…In some hospital laboratories in United Kingdom (UK) as well as in other European countries, after-hours diagnosis of malaria is performed using only immunochromatography-based malaria rapid diagnostic tests (RDTs) [8,12]. A large survey conducted in Belgium and Luxembourg has also shown that one third of participant laboratories used RDTs alone for malaria diagnosis although this is not a recommended practice [9]. Although RDTs are rapid, easy to use and sensitive for P. falciparum, they lack sensitivity at low parasite density, fail to identify a large number of non-falciparum malaria, do not allow parasite quantification, are prone to some errors in reading and interpreting test lines and result in false negative malaria diagnosis when P. falciparum with Histidine Rich Protein 2 (HRP2)-deletion is involved [6,9,10,13].…”

“…A large survey conducted in Belgium and Luxembourg has also shown that one third of participant laboratories used RDTs alone for malaria diagnosis although this is not a recommended practice [9]. Although RDTs are rapid, easy to use and sensitive for P. falciparum, they lack sensitivity at low parasite density, fail to identify a large number of non-falciparum malaria, do not allow parasite quantification, are prone to some errors in reading and interpreting test lines and result in false negative malaria diagnosis when P. falciparum with Histidine Rich Protein 2 (HRP2)-deletion is involved [6,9,10,13]. At present, PCR represents the most sensitive and specific tool for the diagnosis of malaria, but its cost and turnaround time greatly limit its use outside of reference laboratories [11,[14][15][16].…”