External Quality Assessment in the Examination of Blood Films for Malarial Parasites
Bibliographic record
Abstract
To the Editor.—The article by Thomson et al,1 “External Quality Assessment in the Examination of Blood Films for Malarial Parasites Within Ontario, Canada,” correctly identified a significant and potentially serious problem in malaria speciation. However, I am bewildered by their statement “These and other studies support the need for prompt examination of thick and thin blood films … ,” when their data provide a strong argument for abandoning thick films. Whereas there is no significant difference in the rate of false positives when thick and thin films are compared, the false-negative rate for thick films is 17 times higher than that for thin films. Unfortunately, the authors do not provide data that allow one to determine whether speciation was facilitated by the examination of thick films. However, it would be my experience and educated guess that speciation, as well, was better performed in thin films than thick films.I found it encouraging that a significant number of laboratories had shown the good sense to abandon the thick film preparation and examination despite obsolete recommendations and even accreditation requirements to the contrary. Virtually all modern laboratories have individuals skilled at preparing and interpreting thin blood smears. Very few have people with the skills to make good quality thick films or to interpret them. We should capitalize on our areas of strength. It makes no sense to continue to encourage shortcutting, the original intent in the preparation of thick films.Sam Thomson BA, ARTMDS Laboratory Services Kitchener, Ontario, Canada N2M 5N4Reinhard C. Lohmann MD, FRCPCLondon Health Sciences Centre London, Ontario, Canada N6A 4G5Linda Crawford MT(ASCP); Ruby Dubash; Harold Richardson MD, FRCPCLaboratory Proficiency Testing Program Toronto, Ontario, Canada M4W 1E6In Reply. Dr Sheehan questions the value of preparing and interpreting thick films for malarial parasites largely on the basis of lack of technical expertise. We are fully aware of these difficulties. However, it was not the purpose of our review to examine the value of the thick film versus the thin film.We do not believe that our results infer that “the false-negative rate for thick films is 17 times higher than that for thin films.” Nor did we discuss the value, if any, of thick films in malaria speciation. As stated in our article, scanty parasites and Plasmodium falciparum gametocytes may be easier to detect in thick films and therefore might be of value in low infections and in P falciparum speciation.It would be of interest to test scientifically the accuracy of the thick film in low-level parasitemia compared to the thin film. Until such time, we believe that prompt examination of both thick and thin films is advisable.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.013 | 0.083 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.002 | 0.004 |
| Scholarly communication | 0.005 | 0.004 |
| Open science | 0.005 | 0.001 |
| Research integrity | 0.012 | 0.014 |
| Insufficient payload (model declined to judge) | 0.004 | 0.003 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".