External quality assessment on the use of malaria rapid diagnostic tests in a non-endemic setting

Magneto-optical diagnosis of symptomatic malaria in Papua New Guinea

Improved methods for malaria diagnosis are urgently needed. Here, we evaluate a novel method named rotating-crystal magneto-optical detection (RMOD) in 956 suspected malaria patients in Papua New Guinea. RMOD tests can be conducted within minutes and at low cost. We systematically evaluate the capability of RMOD to detect infections by directly comparing it with expert light microscopy, rapid diagnostic tests and polymerase chain reaction on capillary blood samples. We show that compared to light microscopy, RMOD exhibits 82% sensitivity and 84% specificity to detect any malaria infection and 87% sensitivity and 88% specificity to detect Plasmodium vivax. This indicates that RMOD could be useful in P. vivax dominated elimination settings. Parasite density correlates well with the quantitative magneto-optical signal. Importantly, residual hemozoin present in malaria-negative patients is also detectable by RMOD, indicating its ability to detect previous infections. This could be exploited to reveal transmission hotspots in low-transmission settings.

Here Arndt et al. establish rotating-crystal magneto-optical detection (RMOD) as a near-point-of-care diagnostic tool for malaria detection and report a sensitivity and specificity of 82% and 84%, respectively, as validated by analyzing a clinical population in a high transmission setting in Papua New Guinea.

A comparative evaluation of mobile medical APPS (MMAS) for reading and interpreting malaria rapid diagnostic tests

BACKGROUND

The World Health Organization recommends confirmatory diagnosis by microscopy or malaria rapid diagnostic test (RDT) in patients with suspected malaria. In recent years, mobile medical applications (MMAs), which can interpret RDT test results have entered the market. To evaluate the performance of commercially available MMAs, an evaluation was conducted by comparing RDT results read by MMAs to RDT results read by the human eye.

METHODS

Five different MMAs were evaluated on six different RDT products using cultured Plasmodium falciparum blood samples at five dilutions ranging from 20 to 1000 parasites (p)/microlitre (µl) and malaria negative blood samples. The RDTs were performed in a controlled, laboratory setting by a trained operator who visually read the RDT results. A second trained operator then used the MMAs to read the RDT results. Sensitivity (Sn) and specificity (Sp) for the RDTs were calculated in a Bayesian framework using mixed models.

RESULTS

The RDT Sn of the P. falciparum (Pf) test line, when read by the trained human eye was significantly higher compared to when read by MMAs (74% vs. average 47%) at samples of 20 p/µl. In higher density samples, the Sn was comparable to the human eye (97%) for three MMAs. The RDT Sn of test lines that detect all Plasmodium species (Pan line), when read by the trained human eye was significantly higher compared to when read by MMAs (79% vs. average 56%) across all densities. The RDT Sp, when read by the human eye or MMAs was 99% for both the Pf and Pan test lines across all densities.

CONCLUSIONS

The study results show that in a laboratory setting, most MMAs produced similar results interpreting the Pf test line of RDTs at parasite densities typically found in patients that experience malaria symptoms (> 100 p/µl) compared to the human eye. At low parasite densities for the Pf line and across all parasite densities for the Pan line, MMAs were less accurate than the human eye. Future efforts should focus on improving the band/line detection at lower band intensities and evaluating additional MMA functionalities like the ability to identify and classify RDT errors or anomalies.

Accuracy of malaria diagnosis by clinical laboratories in Belgium

BACKGROUND

The Belgian Reference Laboratory for Plasmodium offers a free-of-charge reference testing of malaria-positive or doubtful samples to clinical laboratories.

METHODS

The final malaria diagnosis from the Reference Laboratory (microscopy, rapid diagnostic tests (RDTs) and Plasmodium species-specific PCR) were compared with the final diagnosis from peripheral Belgian laboratories. The Reference Laboratory reports were analysed for all samples submitted between 2013 and 2017. Criteria assessed included the diagnosis of malaria, Plasmodium species identification including mixed infections, and in case of Plasmodium falciparum, the parasite density and the presence of sexual and asexual stages.

RESULTS

A total of 947 non-duplicate samples were included. Reference testing confirmed 96.3% (893/927) and 90.0% (18/20) samples submitted as positive and negative, respectively, the two missed diagnoses were samples with Plasmodium ovale and Plasmodium malariae. Submitting laboratories had correctly identified P. falciparum in 95.1% (508/534) samples with P. falciparum single infection. They had correctly diagnosed the species in 62.9% (95/151) single non-falciparum samples and had reported 'non-falciparum' in another 26 (17.2%) samples; most errors occurred among P. malariae (n = 8/21, 38.1%) and P. ovale (n = 14/51, 27.5%). Only one of the 21 mixed Plasmodium species infections had been diagnosed as such by the submitting laboratories; in three of them, P. falciparum had been overlooked. Taken single and mixed infections together, P. falciparum was diagnosed in 98.6% (546/554) samples. Among 471 single P. falciparum samples available for comparison, laboratories had correctly reported parasite densities above 2% in 87.5% (70/80) samples; they had incorrectly reported parasite densities > 2% in an extra 52 (8.9%) samples. Laboratories had correctly reported P. falciparum schizonts and gametocytes in 25.6% (11/43) and 56.7% (17/30) samples, respectively.

CONCLUSION

Diagnostic laboratories in a malaria non-endemic setting provided excellent diagnosis of malaria and P. falciparum, reasonably good diagnosis of non-falciparum infections and acceptable calculation of P. falciparum parasite density.

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

Introduction

In non-endemic settings, expertise in malaria microscopy is limited and rapid diagnostic tests (RDTs) are an adjunct to malaria diagnosis.

Aim

We performed an External Quality Assessment (EQA) on reading and interpretation of malaria RDTs in a non-endemic setting.

Methods

Participants 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.

Results

Among 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.

Conclusion

Reading 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.

External quality assessment in resource-limited countries

Introduction

Health laboratory services are a critical component of national health systems but face major operational challenges in resource-limited (RL) settings. New funding for health systems strengthening in RL countries has increased the demand for diagnostics and provided opportunities to address these constraints. An approach to sustainably strengthen national laboratory systems in sub-Saharan African countries is the Strengthening Laboratory Management Toward Accreditation (SLMTA) programme. External Quality Assessment (EQA) is a requirement for laboratory accreditation. EQA comprises proficiency testing (PT), rechecking of samples and on-site evaluation.

Materials and methods

A systematic literature search was conducted to identify studies addressing laboratory EQA and quality monitoring in RL countries. Unpublished reports were also sought from national laboratory authorities and personnel.

Results

PT schemes in RL countries are provided by commercial companies, institutions in developed countries and national programmes. Most government-supported PT schemes address single diseases using a vertical approach. Regional approaches to delivering PT have also been implemented across RL countries. Rechecking schemes address mainly tuberculosis (TB), malaria and human immunodeficiency virus (HIV); integrated rechecking programmes have been piloted. Constraints include sample transportation, communication of results, unknown proficiency of referee staff and limited resources for corrective action. Global competency assessment standards for malaria microscopists have been established.

Conclusions

EQA is vital for monitoring laboratory performance and maintaining quality of laboratory services, and is a valuable tool for identifying and assessing technology in use, identifying gaps in laboratory performance and targeting training needs. Accreditation of PT providers and competency of EQA personnel must be ensured.

Quality issues with malaria rapid diagnostic test accessories and buffer packaging: findings from a 5-country private sector project in Africa

Background

Use of antigen-detecting malaria rapid diagnostic tests (RDTs) has increased exponentially over the last decade. WHO’s Global Malaria Programme, FIND, and other collaborators have established a quality assurance scheme to guide product selection, lot verification, transport, storage, and training procedures. Recent concerns over the quality of buffer packaging and test accessories suggest a need to include these items in product assessments. This paper describes quality problems with buffer and accessories encountered in a project promoting private sector RDT use in five African countries and suggests steps to avoid or more rapidly identify and resolve such problems.

Methods

Private provider complaints about RDT buffer vials and kit accessories were collected during supervisory visits, and a standard assessment process was developed. Using 100 tests drawn from six different lots produced by two manufacturers, lab technicians visually assessed alcohol swab packaging, blood transfer device (BTD) usability, and buffer appearance, then calculated mean blood volume from 10 BTD transfers and mean buffer volume from 10 individual buffer vials. WHO guided complaint reporting and follow-up with manufacturers.

Results

Supervisory visits confirmed user reports of dry alcohol swabs, poorly functioning BTDs, and non-uniform volumes of buffer. Lot testing revealed further evidence of quality problems, leading one manufacturer to replace buffer vials and accessories for 40,000 RDTs. In December 2014, WHO issued an Information Notice for Users regarding variable buffer volumes in single-use vials and recommended against procurement of these products until defects were addressed.

Discussion

Though not necessarily comprehensive or generalizable, the findings presented here highlight the need for extending quality assessment to all malaria RDT test kit contents. Defects such as those described in this paper could reduce test accuracy and increase probability of invalid, false positive, or false negative results. Such deficiencies could undermine provider confidence in RDTs, prompting a return to presumptive treatment or reliance on poor quality microscopy. In partial response to this experience, WHO, FIND, and other project partners have developed guidance on documenting, troubleshooting, reporting, and resolving such problems when they occur.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-017-1820-1) contains supplementary material, which is available to authorized users.

Cost benefit analysis of malaria rapid diagnostic test: the perspective of Nigerian community pharmacists

Background

In 2010, the World Health Organization issued a guideline that calls for a shift from presumptive to test-based treatment. However, test-based treatment is still unpopular in community pharmacies. This could be due to unwillingness of customers to spend extra finance on rapid diagnostic test (RDT). It could also result from lack of interest from community pharmacists since they may perceive no financial gain attached to this service. This study assessed the cost-benefit of test-based malaria treatment to community pharmacists.

Methods

The study was a community pharmacy-based cross sectional survey. Potential benefit of RDT was determined using customers’ willingness-to-pay (WTP) for service. Average WTP was estimated using contingent valuation. Binary logistic regression was used to assess correlates of WTP acceptance while multiple linear regression was used to model the relationship between the independent variables and WTP amount. Cost associated with provision of RDT was estimated from provider’s perspective. Probabilistic sensitivity analysis was used to capture parameter uncertainty. Benefit-cost ratio (BCR) was calculated to determine study objective.

Results

A total of 135 out of 235 participants (57.4%) responded to the WTP question. Of this subset, 111 participants (82.2%) preferred RDT before malaria treatment. Average WTP [minimum–maximum] was US$1.23 [US$0.0–US$5.03]. Educated participants had 1.8 times higher odds of WTP for RDT. Participants that understood RDT as described in the questionnaire had 18.3 times higher odds of WTP for RDT compared to participants that did not understand RDT as described in the questionnaire. Additionally, a unit increase in level of education (e.g. from primary to secondary school) led to US$0.298 increase in WTP amount for RDT. Also, a unit increase in malaria frequency (e.g. from ‘never’ to ‘rarely’) led to US$0.293 decrease in WTP amount for RDT. Average cost [minimum–maximum] of RDT test kit and pharmacist time spent in administering the test were US$0.15 [US$0.13–US$0.17] and US$0.41 [US$0.18–US$0.52], respectively. BCR of test-based malaria treatment was 6.7 (95% CI 6.4–7.0).

Conclusion

Test-based malaria treatment is cost-beneficial for pharmacy practitioners. This finding could be used as an advocacy tool to increase community pharmacists’ interest and uptake of test-based malaria treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-016-1648-0) contains supplementary material, which is available to authorized users.

Quality assurance for HIV point-of-care testing and treatment monitoring assays

In 2015, UNAIDS launched the 90-90-90 targets aimed at increasing the number of people infected with HIV to become aware of their status, access antiretroviral therapies and ultimately be virally suppressed. To achieve these goals, countries may need to scale up point-of-care (POC) testing in addition to strengthening central laboratory services. While decentralising testing increases patient access to diagnostics, it presents many challenges with regard to training and assuring the quality of tests and testing. To ensure synergies, the London School of Hygiene & Tropical Medicine held a series of consultations with countries with an interest in quality assurance and their implementing partners, and agreed on an external quality assessment (EQA) programme to ensure reliable results so that the results lead to the best possible care for HIV patients. As a result of the consultations, EQA International was established, bringing together EQA providers and implementers to develop a strategic plan for countries to establish national POC EQA programmes and to estimate the cost of setting up and maintaining the programme. With the dramatic increase in the number of proficiency testing panels required for thousands of POC testing sites across Africa, it is important to facilitate technology transfer from global EQA providers to a network of regional EQA centres in Africa for regional proficiency testing panel production. EQA International will continue to identify robust and cost-effective EQA technologies for quality POC testing, integrating novel technologies to support sustainable country-owned EQA programmes in Africa.

Replacing antibodies with aptamers in lateral flow immunoassay

Aptamers have been identified against various targets as a type of chemical or nucleic acid ligand by systematic evolution of ligands by exponential enrichment (SELEX) with high sensitivity and specificity. Aptamers show remarkable advantages over antibodies due to the nucleic acid nature and target-induced structure-switching properties and are widely used to design various fluorescent, electrochemical, or colorimetric biosensors. However, the practical applications of aptamer-based sensing and diagnostics are still lagging behind those of antibody-based tests. Lateral flow immunoassay (LFIA) represents a well established and appropriate technology among rapid assays because of its low cost and user-friendliness. The antibody-based platform is utilized to detect numerous targets, but it is always hampered by the antibody preparation time, antibody stability, and effect of modification on the antibody. Seeking alternatives to antibodies is an area of active research and is of tremendous importance. Aptamers are receiving increasing attention in lateral flow applications because of a number of important potential performance advantages. We speculate that aptamer-based LFIA may be one of the first platforms for commercial use of aptamer-based diagnosis. This review first gives an introduction to aptamer including the selection process SELEX with its focus on aptamer advantages over antibodies, and then depicts LFIA with its focus on aptamer opportunities in LFIA over antibodies. Furthermore, we summarize the recent advances in the development of aptamer-based lateral flow biosensing assays with the aim to provide a general guide for the design of aptamer-based lateral flow biosensing assays.

Field application of SD bioline malaria Ag Pf/Pan rapid diagnostic test for malaria in Greece

Greece, a malaria-free country since 1974, has experienced re-emergence of Plasmodium vivax autochthonous malaria cases in some agriculture areas over the last three years. In early 2012, an integrated control programme (MALWEST Project) was launched in order to prevent re-establishment of the disease. In the context of this project, the rapid diagnostic tests (RDT) of SD Bioline Malaria Ag Pf/Pan that detects hrp-2 and pan-LDH antigens were used. The aim of this study was to assess the field application of the RDT for the P. vivax diagnosis in comparison to light microscopy and polymerase chain reaction (PCR). A total of 955 samples were tested with all three diagnostic tools. Agreement of RDT against microscopy and PCR for the diagnosis of P. vivax was satisfactory (K value: 0.849 and 0.976, respectively). The sensitivity, specificity and positive predictive value of RDT against PCR was 95.6% (95% C.I.: 84.8-99.3), 100% (95% C.I.: 99.6-100.0) and 100% (95% CI: 91.7-100.0) respectively, while the sensitivity, specificity and positive predictive value of RDT against microscopic examination was 97.4% (95% C.I.: 86.1-99.6), 99.4% (95% C.I.: 98.6-99.8) and 86.1% (95% CI: 72.1-94.7), respectively. Our results indicate that RDT performed satisfactory in a non-endemic country and therefore is recommended for malaria diagnosis, especially in areas where health professionals lack experience on light microscopy.

SMS photograph-based external quality assessment of reading and interpretation of malaria rapid diagnostic tests in the Democratic Republic of the Congo

Background

The present External Quality Assessment (EQA) assessed reading and interpretation of malaria rapid diagnostic tests (RDTs) in the Democratic Republic of the Congo (DRC).

Methods

The EQA consisted of (i) 10 high-resolution printed photographs displaying cassettes with real-life results and multiple choice questions (MCQ) addressing individual health workers (HW), and (ii) a questionnaire on RDT use addressing the laboratory of health facilities (HF). Answers were transmitted through short message services (SMS).

Results

The EQA comprised 2344 HW and 1028 HF covering 10/11 provinces in DRC. Overall, median HW score (sum of correct answers on 10 MCQ photographs for each HW) was 9.0 (interquartile range 7.5 – 10); MCQ scores (the % of correct answers for a particular photograph) ranged from 54.8% to 91.6%. Most common errors were (i) reading or interpreting faint or weak line intensities as negative (3.3%, 7.2%, 24.3% and 29.1% for 4 MCQ photographs), (ii) failure to distinguish the correct Plasmodium species (3.4% to 7.0%), (iii) missing invalid test results (8.4% and 23.6%) and (iv) missing negative test results (10.0% and 12.4%). HW who were trained less than 12 months ago had best MCQ scores for 7/10 photographs as well as a significantly higher proportion of 10/10 scores, but absolute differences in MCQ scores were small. HW who had participated in a previous EQA performed significantly better for 4/10 photographs compared to those who had not. Except for two photographs, MCQ scores were comparable for all levels of the HF hierarchy and non-laboratory staff (HW from health posts) had similar performance as to laboratory staff. Main findings of the questionnaire were (i) use of other RDT products than recommended by the national malaria control programme (nearly 20% of participating HF), (ii) lack of training for a third (33.6%) of HF, (iii) high proportions (two-thirds, 66.5%) of HF reporting stock-outs.

Conclusions

The present EQA revealed common errors in RDT reading and interpretation by HW in DRC. Performances of non-laboratory and laboratory staff were similar and dedicated training was shown to improve HW competence although to a moderate extent. Problems in supply, distribution and training of RDTs were detected.

The implementation of an external quality assurance method for point- of- care tests for HIV and syphilis in Tanzania

Background

External quality assurance (EQA) programmes, which are routinely used in laboratories, have not been widely implemented for point-of- care tests (POCTs). A study was performed in ten health centres in Tanzania, to implement the use of dried blood spots (DBS) as an EQA method for HIV and syphilis (POCTs).

Method

DBS samples were collected for retesting at a reference laboratory and the results compared to the POCT results obtained at the clinic. In total, 2341 DBS samples were collected from 10 rural health facilities over a period of nine months, of which 92.5% were correctly collected and spotted.

Results

The EQA method was easily implemented by healthcare workers under routine conditions in Northern Tanzania. For HIV, 967 out of 972 samples (99.5%) were concordant between DBS and POCT results. For syphilis, the sensitivity of syphilis tests varied between clinics with a median of 96% (25^th and 75^th quartile; 95-98%). The specificity of syphilis POCT was consistent compared to laboratory based test using DBS, with a median of 96% (25^th and 75^th quartiles; 95-98%).

Conclusion

Overall, the quality of testing varied at clinics and EQA results can be used to identify clinics where healthcare workers require remedial training, suggesting the necessity for stringent quality assurance programmes for POC testing. As Tanzania embarks on scaling up HIV and syphilis testing, DBS can be a useful and robust tool to monitor the quality of testing performed by healthcare workers and trigger corrective action to ensure accuracy of test results.

Malaria rapid diagnostic tests: challenges and prospects

In the last decade, there has been an upsurge of interest in developing malaria rapid diagnostic test (RDT) kits for the detection of Plasmodium species. Three antigens - Plasmodium falciparum histidine-rich protein 2 (PfHRP2), plasmodial aldolase and plasmodial lactate dehydrogenase (pLDH) - are currently used for RDTs. Tests targeting HRP2 contribute to more than 90% of the malaria RDTs in current use. However, the specificities, sensitivities, numbers of false positives, numbers of false negatives and temperature tolerances of these tests vary considerably, illustrating the difficulties and challenges facing current RDTs. This paper describes recent developments in malaria RDTs, reviewing RDTs detecting PfHRP2, pLDH and plasmodial aldolase. The difficulties associated with RDTs, such as genetic variability in the Pfhrp2 gene and the persistence of antigens in the bloodstream following the elimination of parasites, are discussed. The prospect of overcoming the problems associated with current RDTs with a new generation of alternative malaria antigen targets is also described.

External quality assessment of reading and interpretation of malaria rapid diagnostic tests among 1849 end-users in the Democratic Republic of the Congo through Short Message Service (SMS)

Background

Although malaria rapid diagnostic tests (RDT) are simple to perform, they remain subject to errors, mainly related to the post-analytical phase. We organized the first large scale SMS based external quality assessment (EQA) on correct reading and interpretation of photographs of a three-band malaria RDT among laboratory health workers in the Democratic Republic of the Congo (DR Congo).

Methods and Findings

High resolution EQA photographs of 10 RDT results together with a questionnaire were distributed to health facilities in 9 out of 11 provinces in DR Congo. Each laboratory health worker answered the EQA by Short Message Service (SMS). Filled-in questionnaires from each health facility were sent back to Kinshasa. A total of 1849 laboratory health workers in 1014 health facilities participated. Most frequent errors in RDT reading were i) failure to recognize invalid (13.2–32.5% ) or negative test results (9.8–12.8%), (ii) overlooking faint test lines (4.1–31.2%) and (iii) incorrect identification of the malaria species (12.1–17.4%). No uniform strategy for diagnosis of malaria at the health facility was present. Stock outs of RDTs occurred frequently. Half of the health facilities had not received an RDT training. Only two thirds used the RDT recommended by the National Malaria Control Program. Performance of RDT reading was positively associated with training and the technical level of health facility. Facilities with RDT positivity rates >50% and located in Eastern DR Congo performed worse.

Conclusions

Our study confirmed that errors in reading and interpretation of malaria RDTs are widespread and highlighted the problem of stock outs of RDTs. Adequate training of end-users in the application of malaria RDTs associated with regular EQAs is recommended.

Self-diagnosis of malaria by travelers and expatriates: assessment of malaria rapid diagnostic tests available on the internet

Introduction

In the past malaria rapid diagnostic tests (RDTs) for self-diagnosis by travelers were considered suboptimal due to poor performance. Nowadays RDTs for self-diagnosis are marketed and available through the internet. The present study assessed RDT products marketed for self-diagnosis for diagnostic accuracy and quality of labeling, content and instructions for use (IFU).

Methods

Diagnostic accuracy of eight RDT products was assessed with a panel of stored whole blood samples comprising the four Plasmodium species (n = 90) as well as Plasmodium negative samples (n = 10). IFUs were assessed for quality of description of procedure and interpretation and for lay-out and readability level. Errors in packaging and content were recorded.

Results

Two products gave false-positive test lines in 70% and 80% of Plasmodium negative samples, precluding their use. Of the remaining products, 4/6 had good to excellent sensitivity for the diagnosis of Plasmodium falciparum (98.2%–100.0%) and Plasmodium vivax (93.3%–100.0%). Sensitivity for Plasmodium ovale and Plasmodium malariae diagnosis was poor (6.7%–80.0%). All but one product yielded false-positive test lines after reading beyond the recommended reading time. Problems with labeling (not specifying target antigens (n = 3), and content (desiccant with no humidity indicator (n = 6)) were observed. IFUs had major shortcomings in description of test procedure and interpretation, poor readability and lay-out and user-unfriendly typography. Strategic issues (e.g. the need for repeat testing and reasons for false-negative tests) were not addressed in any of the IFUs.

Conclusion

Diagnostic accuracy of RDTs for self-diagnosis was variable, with only 4/8 RDT products being reliable for the diagnosis of P. falciparum and P. vivax, and none for P. ovale and P. malariae. RDTs for self-diagnosis need improvements in IFUs (content and user-friendliness), labeling and content before they can be considered for self-diagnosis by the traveler.

Evaluation of the malaria rapid diagnostic test SDFK90: detection of both PfHRP2 and Pf-pLDH

Background

Rapid diagnosis of Plasmodium falciparum infections is important because of the potentially fatal complications. SDFK90 is a recently marketed malaria rapid diagnostic test (RDT) targeting both histidine-rich protein 2 (PfHRP2) and P. falciparum-specific Plasmodium lactate dehydrogenase (Pf-pLDH). The present study evaluated its diagnostic accuracy.

Methods

SDFK90 was tested against a panel of stored whole blood samples (n= 591) obtained from international travellers suspected of malaria, including the four human Plasmodium species and Plasmodium negative samples. Microscopy was used as a reference method, corrected by PCR for species diagnosis. In addition, SDFK90 was challenged against 59 P. falciparum samples with parasite density ≥4% to assess the prozone effect (no or weak visible line on initial testing and a higher intensity upon 10-fold dilution).

Results

Overall sensitivity for the detection of P. falciparum was 98.5% and reached 99.3% at parasite densities >100/μl. There were significantly more PfHRP2 lines visible compared to Pf-pLDH (97.3% vs 86.9%), which was mainly absent at parasite densities <100/μl. Specificity of SDFK90 was 98.8%. No lot-to-lot variability was observed (p = 1.00) and test results were reproducible. A prozone effect was seen for the PfHRP2 line in 14/59 (23.7%) P. falciparum samples tested, but not for the Pf-pLDH line. Few minor shortcomings were observed in the kit’s packaging and information insert.

Conclusions

SDFK90 performed excellent for P. falciparum diagnosis. The combination of PfHRP2 and Pf-pLDH ensures a low detection threshold and counters potential problems of PfHRP2 detection such as gene deletions and the prozone effect.

Evaluation of the rapid diagnostic test CareStart pLDH Malaria (Pf-pLDH/pan-pLDH) for the diagnosis of malaria in a reference setting

BACKGROUND

The present study evaluated CareStart pLDH Malaria, a three-band rapid diagnostic test detecting Plasmodium falciparum-specific parasite lactate dehydrogenase (Pf-pLDH) and pan Plasmodium-specific pLDH (pan-pLDH) in a reference setting.

METHODS

CareStart pLDH was retrospectively and prospectively assessed with a panel of stored (n=498) and fresh (n=77) blood samples obtained in international travelers suspected of malaria. Both panels comprised all four Plasmodium species; the retrospective panel comprised also Plasmodium negative samples. The reference method was microscopy corrected by PCR. The prospective panel was run side-to-side with OptiMAL (Pf-pLDH/pan-pLDH) and SDFK60 (histidine-rich protein-2 (HRP-2)/pan-pLDH).

RESULTS

In the retrospective evaluation, overall sensitivity for P. falciparum samples (n=247) was 94.7%, reaching 98.7% for parasite densities>1,000/μl. Most false negative results occurred among samples with pure gametocytaemia (2/12, 16.7%) and at parasite densities ≤ 100/μl (7/12, 58.3%). None of the Plasmodium negative samples (n=96) showed visible test lines. Sensitivities for Plasmodium vivax (n=70), Plasmodium ovale (n=69) and Plasmodium malariae (n=16) were 74.3%, 31.9% and 25.0% respectively. Wrong species identification occurred in 10 (2.5%) samples and was mainly due to P. vivax samples reacting with the Pf-pLDH test line. Overall, Pf-pLDH test lines showed higher line intensities compared to the pan-pLDH lines (67.9% and 23.0% medium and strong line intensities for P. falciparum). In the prospective panel (77 Plasmodium-positive samples), CareStart pLDH showed higher sensitivities for P. falciparum compared to OptiMAL (p=0.008), lower sensitivities for P. falciparum as compare to SDFK60 (although not reaching statistical significance, p=0.08) and higher sensitivities for P. ovale compared to both OptiMAL (p=0.03) and SDFK60 (p=0.01). Inter-observer and test reproducibility were good to excellent.

CONCLUSION

CareStart pLDH performed excellent for the detection of P. falciparum, well for P. vivax, but poor for P. ovale and P. malariae.

State of malaria diagnostic testing at clinical laboratories in the United States, 2010: a nationwide survey

Background

The diagnosis of malaria can be difficult in non-endemic areas, such as the United States, and delays in diagnosis and errors in treatment occur too often.

Methods

A nationwide survey of laboratories in the United States and its nine dependent territories was conducted in 2010 to determine factors that may contribute to shortcomings in the diagnosis of malaria. This survey explored the availability of malaria diagnostic tests, techniques used, and reporting practices.

Results

The survey was completed by 201 participants. Ninety percent reported that their laboratories had at least one type of malaria diagnostic test available on-site. Nearly all of the respondents' laboratories performed thick and thin smears on-site; approximately 50% had access to molecular testing; and only 17% had access to rapid diagnostic tests on-site. Seventy-three percent reported fewer than five confirmed cases of malaria in their laboratory during the 12-month period preceding the survey. Twenty-eight percent stated that results of species identification took more than 24 hours to report. Only five of 149 respondents that performed testing 24 hours a day, 7 days a week complied with all of the Clinical and Laboratory Standards Institute (CLSI) guidelines for analysis and reporting of results.

Conclusion

Although malaria diagnostic testing services were available to a majority of U.S. laboratories surveyed, very few were in complete compliance with all of the CLSI guidelines for analysis and reporting of results, and most respondents reported very few cases of malaria annually. Laboratories' difficulty in adhering to the rigorous CLSI guidelines and their personnel's lack of practice and proficiency may account for delays and errors in diagnosis. It is recommended that laboratories that infrequently process samples for malaria seek opportunities for practice and proficiency training annually and take advantage of available resources to assist in species identification.

External quality assessment of malaria microscopy in the Democratic Republic of the Congo

BACKGROUND

External quality assessments (EQA) are an alternative to cross-checking of blood slides in the quality control of malaria microscopy. This study reports the findings of an EQA of malaria microscopy in the Democratic Republic of the Congo (DRC).

METHODS

After validation, an EQA slide panel and a questionnaire were delivered to diagnostic laboratories in four provinces of DRC. The panel included three samples for diagnosis (sample 1: Plasmodium falciparum, 177,000/μl, sample 2: P. falciparum, 2,500/μl, sample 3: no parasites seen), one didactic sample (Howell-Jolly bodies) and one sample for assessing the quality of staining. Participating laboratories were addressed and selected through the network of the National Tuberculosis Control Programme. Participants were asked to return the responses together with a stained thin and thick blood film for evaluation of Giemsa stain quality.

RESULTS

Among 174 participants (response rate 95.1%), 26.2% scored samples 1, 2 and 3 correctly and 34.3%, 21.5% and 5.8% of participants reported major errors in one, two or three samples respectively. Major errors included reporting "no malaria" or "non-falciparum malaria" for Plasmodium falciparum-positive samples 1 and 2 (16.1% and 34.9% of participants respectively) and "P. falciparum" for Plasmodium negative sample 3 (24.0%). Howell-Jolly bodies (didactic sample) were not recognized by any of the participants but reported as "P. falciparum" by 16.7% of participants. With parasite density expressed according to the "plus system", 16.1% and 21.5% of participants scored one "+" different from the reference score for samples 1 and 2 respectively and 9.7% and 2.9% participants scored more than two "+" different. When expressed as counts of asexual parasites/μl, more than two-thirds of results were outside the mean ± 2SD reference values. The quality of the Giemsa stain was poor, with less than 20% slides complying with all criteria assessed. Only one quarter of participants purchase Giemsa stain from suppliers of documented reliability and half of participants use a buffered staining solution. One third of participants had participated in a formal training about malaria diagnosis, half of them earlier than 2007.

CONCLUSION

The present EQA revealed a poor quality of malaria microscopy in DRC.

Quality of medical devices and in vitro diagnostics in resource-limited settings

The phenomenon of poor-quality medicines in resource-limited settings is well documented, and field observations reveal similar problems with medical devices (MDs) and in vitro diagnostics (IVDs). In scientific literature, however, there are only scarce reports and documents providing evidence of quality problems of MDs or IVDs in resource-limited settings. This discrepancy may be ascribed to (i) the poor regulatory oversight of MDs/IVDs in resource-limited settings, (ii) a general lack of awareness of the problem of poor-quality MDs/IVDs amongst the scientific community and decision-makers, and (iii) poor quality assurance in diagnostic laboratories in resource-poor settings, precluding tracing quality problems of IVDs from the other potential causes of diagnostic inaccuracy. The problem of poor-quality MDs/IVDs in resource-limited settings is a complex one to address. Firstly, operational definitions for substandard and counterfeit MDs/IVDs are required, as well as ad hoc field surveys, to ensure proper appraisal of the real extent of the problem. Investments are needed to reinforce the national regulatory oversights on MDs/IVDs in resource-limited settings, and to encourage a proactive and transparent exchange of information between Northern and Southern regulatory authorities. Industrialized countries can play a role by expanding and strengthening their regulatory oversight and quality labels to those MDs/IVDs that are frequently used in resource-poor settings. Hopefully, the combination of these measures will result in better protection of patients in resource-poor countries from the effects of being exposed to poor-quality MDs and IVDs.

Prozone in malaria rapid diagnostics tests: how many cases are missed?

Background

Prozone means false-negative or false-low results in antigen-antibody reactions, due to an excess of either antigen or antibody. The present study prospectively assessed its frequency for malaria rapid diagnostic tests (RDTs) and Plasmodium falciparum samples in an endemic field setting.

Methods

From January to April 2010, blood samples with P. falciparum high parasitaemia (≥ 4% red blood cells infected) were obtained from patients presenting at the Provincial Hospital of Tete (Mozambique). Samples were tested undiluted and 10-fold diluted in saline with a panel of RDTs and results were scored for line intensity (no line visible, faint, weak, medium and strong). Prozone was defined as a sample which showed no visible test line or a faint or weak test line when tested undiluted, and a visible test line of higher intensity when tested 10-fold diluted, as observed by two blinded observers and upon duplicate testing.

Results

A total of 873/7,543 (11.6%) samples showed P. falciparum, 92 (10.5%) had high parasitaemia and 76 were available for prozone testing. None of the two Pf-pLDH RDTs, but all six HRP-2 RDTs showed prozone, at frequencies between 6.7% and 38.2%. Negative and faint HRP-2 lines accounted for four (3.8%) and 15 (14.4%) of the 104 prozone results in two RDT brands. For the most affected brand, the proportions of prozone with no visible or faint HRP-2 lines were 10.9% (CI: 5.34-19.08), 1.2% (CI: 0.55-2.10) and 0.1% (CI: 0.06-0.24) among samples with high parasitaemia, all positive samples and all submitted samples respectively. Prozone occurred mainly, but not exclusively, among young children.

Conclusion

Prozone occurs at different frequency and intensity in HRP-2 RDTs and may decrease diagnostic accuracy in the most affected RDTs.

Rapid diagnostic tests as a source of DNA for Plasmodium species-specific real-time PCR

Background

This study describes the use of malaria rapid diagnostic tests (RDTs) as a source of DNA for Plasmodium species-specific real-time PCR.

Methods

First, the best method to recover DNA from RDTs was investigated and then the applicability of this DNA extraction method was assessed on 12 different RDT brands. Finally, two RDT brands (OptiMAL Rapid Malaria Test and SDFK60 malaria Ag Plasmodium falciparum/Pan test) were comprehensively evaluated on a panel of clinical samples submitted for routine malaria diagnosis at ITM. DNA amplification was done with the 18S rRNA real-time PCR targeting the four Plasmodium species. Results of PCR on RDT were compared to those obtained by PCR on whole blood samples.

Results

Best results were obtained by isolating DNA from the proximal part of the nitrocellulose component of the RDT strip with a simple DNA elution method. The PCR on RDT showed a detection limit of 0.02 asexual parasites/μl, which was identical to the same PCR on whole blood. For all 12 RDT brands tested, DNA was detected except for one brand when a low parasite density sample was applied. In RDTs with a plastic seal covering the nitrocellulose strip, DNA extraction was hampered. PCR analysis on clinical RDT samples demonstrated correct identification for single species infections for all RDT samples with asexual parasites of P. falciparum (n = 60), Plasmodium vivax (n = 10), Plasmodium ovale (n = 10) and Plasmodium malariae (n = 10). Samples with only gametocytes were detected in all OptiMAL and in 10 of the 11 SDFK60 tests. None of the negative samples (n = 20) gave a signal by PCR on RDT. With PCR on RDT, higher Ct-values were observed than with PCR on whole blood, with a mean difference of 2.68 for OptiMAL and 3.53 for SDFK60. Mixed infections were correctly identified with PCR on RDT in 4/5 OptiMAL tests and 2/5 SDFK60 tests.

Conclusions

RDTs are a reliable source of DNA for Plasmodium real-time PCR. This study demonstrates the best method of RDT fragment sampling for a wide range of RDT brands in combination with a simple and low cost extraction method, allowing RDT quality control.

Malaria rapid diagnostic kits: quality of packaging, design and labelling of boxes and components and readability and accuracy of information inserts

BACKGROUND

The present study assessed malaria RDT kits for adequate and correct packaging, design and labelling of boxes and components. Information inserts were studied for readability and accuracy of information.

METHODS

Criteria for packaging, design, labelling and information were compiled from Directive 98/79 of the European Community (EC), relevant World Health Organization (WHO) documents and studies on end-users' performance of RDTs. Typography and readability level (Flesch-Kincaid grade level) were assessed.

RESULTS

Forty-two RDT kits from 22 manufacturers were assessed, 35 of which had evidence of good manufacturing practice according to available information (i.e. CE-label affixed or inclusion in the WHO list of ISO13485:2003 certified manufacturers). Shortcomings in devices were (i) insufficient place for writing sample identification (n=40) and (ii) ambiguous labelling of the reading window (n=6). Buffer vial labels were lacking essential information (n=24) or were of poor quality (n=16). Information inserts had elevated readability levels (median Flesch Kincaid grade 8.9, range 7.1-12.9) and user-unfriendly typography (median font size 8, range 5-10). Inadequacies included (i) no referral to biosafety (n=18), (ii) critical differences between depicted and real devices (n=8), (iii) figures with unrealistic colours (n=4), (iv) incomplete information about RDT line interpretations (n=31) and no data on test characteristics (n=8). Other problems included (i) kit names that referred to Plasmodium vivax although targeting a pan-species Plasmodium antigen (n=4), (ii) not stating the identity of the pan-species antigen (n=2) and (iii) slight but numerous differences in names displayed on boxes, device packages and information inserts. Three CE labelled RDT kits produced outside the EC had no authorized representative affixed and the shape and relative dimensions of the CE symbol affixed did not comply with the Directive 98/79/EC. Overall, RDTs with evidence of GMP scored better compared to those without but inadequacies were observed in both groups.

CONCLUSION

Overall, malaria RDTs showed shortcomings in quality of construction, design and labelling of boxes, device packages, devices and buffers. Information inserts were difficult to read and lacked relevant information.

Evaluation of the rapid diagnostic test SDFK40 (Pf-pLDH/pan-pLDH) for the diagnosis of malaria in a non-endemic setting

Background

The present study evaluated the SD Bioline Malaria Ag 05FK40 (SDFK40), a three-band RDT detecting Plasmodium falciparum-specific parasite lactate dehydrogenase (Pf-pLDH) and pan Plasmodium-specific pLDH (pan-pLDH), in a reference setting.

Methods

The SDFK40 was retrospectively and prospectively tested against a panel of stored (n = 341) and fresh (n = 181) whole blood samples obtained in international travelers suspected of malaria, representing the four Plasmodium species as well as Plasmodium negative samples, and compared to microscopy and PCR results. The prospective panel was run together with OptiMAL (Pf-pLDH/pan-pLDH) and SDFK60 (histidine-rich protein-2 (HRP-2)/pan-pLDH).

Results

Overall sensitivities for P. falciparum tested retrospectively and prospectively were 67.9% and 78.8%, reaching 100% and 94.6% at parasite densities >1,000/μl. Sensitivity at parasite densities ≤ 100/μl was 9.1%. Overall sensitivities for Plasmodium vivax and Plasmodium ovale were 86.7% and 80.0% (retrospectively) and 92.9% and 76.9% (prospectively), reaching 94.7% for both species (retrospective panel) at parasite densities >500/μl. Sensitivity for Plasmodium malariae was 21.4%. Species mismatch occurred in 0.7% of samples (3/411) and was limited to non-falciparum species erroneously identified as P. falciparum. None of the Plasmodium negative samples in the retrospective panel reacted positive. Compared to OptiMAL and SDFK60, SDFK40 showed lower sensitivities for P. falciparum, but better detection of P. ovale. Inter-observer agreement and test reproducibility were excellent, but lot-to-lot variability was observed for pan-pLDH results in case of P. falciparum.

Conclusion

SDFK40 performance was poor at low (≤ 100/μl) parasite densities, precluding its use as the only diagnostic tool for malaria diagnosis. SDFK40 performed excellent for P. falciparum samples at high (>1,000/μl) parasite densities as well as for detection of P. vivax and P. ovale at parasite densities >500/μl.

Clinical practice: the diagnosis of imported malaria in children

The present paper reviews the diagnosis of imported malaria in children. Malaria is caused by a parasite called Plasmodium and occurs in over 100 countries worldwide. Children account for 10-15% of all patients with imported malaria and are at risk to develop severe and life-threatening complications especially when infected with Plasmodium falciparum. Case-fatality ratios vary between 0.2% and 0.4%. Children visiting friends and relatives in malaria endemic areas and immigrants and refugees account for the vast majority of cases. Symptoms are non-specific and delayed infections (more than 3 months after return from an endemic country) may occur. Microscopic analysis of the thick blood film is the cornerstone of laboratory diagnosis. For pragmatic reasons, EDTA-anticoagulated blood is accepted, provided that slides are prepared within 1 h after collection. Information about the Plasmodium species (in particular P. falciparum versus the non-falciparum species) and the parasite density is essential for patient management. Molecular methods in reference settings are an adjunct for species differentiation. Signals generated by automated hematology analyzers may trigger the diagnosis of malaria in non-suspected cases. Malaria rapid diagnostic tests are reliable in the diagnosis of P. falciparum but not for the detection of the non-falciparum species. They do not provide information about parasite density and should be used as an adjunct (and not a substitute) to microscopy. In case of persistent suspicion and negative microscopy results, repeat testing every 8-12 h for at least three consecutive samplings is recommended. A high index of suspicion and a close interaction with the laboratory may assure timely diagnosis of imported malaria.